I used to get very frustrated with my companions on my mission. Every time a Born Again Christian would announce that “Mormons believe they have to work their way to heaven” my companion would inevitably argue back “Well you believe that after you accept Christ you can commit any sin you want and still go to heaven.” Trying to separate the combatants and send them to their corners proved impossible.
But Protestant Christians do not believe a person can accept Christ and then go out and commit unrepentant sin and still go to heaven  any more than Mormons believe they have to work their way to heaven.  But what is the difference between the Protestant Christian view of grace and works and the Mormon one?
Pat answers do not help here. Mormons claiming that that they are saved by grace “after all we can do” (2 Nephi 25:23) implies that Protestant Christians think one doesn’t really have to be serious about their commitment to Christ by putting in effort. But my direct experience with them contradicts this belief. Protestants usually do believe one must accept Jesus as Lord and begin to follow His commandments with sincerity. I believe Protestants and Evangelicals, while perhaps rejecting the language, in principle and practice accept the teachings of 2 Nephi 25:23. 
The idea that Mormons believe in the necessity of ordinances while Protestants do not doesn’t really help either. Even the most sacrament/ordinance defying sects of Protestantism still have their own rites that play the same role. For example, going before a minister and declaring your acceptance of Christ so that you “get saved” is really just a saving ordinance to a Mormon viewpoint. If it walks like a duck…
After reading How Wide the Divide? Stephen Robinson about had me convinced that there was actually no difference at all between the Mormon view of salvation and the Arminian view. And yet, I was never able to shake the feeling that there are significant differences between the Mormon and the Protestant views of salvation, but that they are – for some reason – difficult to define or come to agreement on. 
I wish to take my own stab at defining the differences.
Protestant View of Salvation, Grace, and “Works”
Protestants have varied and wide views on this subject, but there seems to be heavy overlap in a few areas. First, one must accept Jesus Christ to be saved.  This salvation comes “only” by grace, because there is nothing we can do — other than accepting Jesus — that affects our salvation.  Once a person accepts Christ they are “Born Again” and changed at that point from an unsaved being that deserved @#!*% to a saved being. This is because God, at the time of the individual accepting Jesus, has now paid for their sins.  As “a new creature” (2 Cor. 5: 17) in Christ the Christian now brings forth “good works” as a way of showing love and gratitude to God. This is part of the new nature God has given them. But these “good works” play no role in how one received salvation in the first place. 
To a Protestant, salvation can be defined as either not going to @#!*% , or going to heaven as these two are really the same thing in the Protestant worldview.
Mormon View of Salvation, Grace, and “Works” (aka Obedience)
So how does the Mormon view of salvation differ? Like Protestants, Mormons do believe one must accept Christ to receive any level of salvation, though admittedly we believe this can be in the afterlife. Mormons would agree with Protestants that a person that accepts Christ is “Born Again” and becomes a new creature in Christ. Mormons agree with Protestants that “obedience” or “works” is something you do out of Lordship to Christ and also because we Love Him. So far, we seem to be in agreement. 
Baptism as Covenant Relationship
But do Mormons believe a person is “saved” when they accept Christ and are “born again”? In a sense, perhaps yes, but it seems to me that the Mormon concept of baptism has less to do with “accepting Jesus” and more to do with “entering into a covenant relationship with Jesus.” (Mosiah 5:5) Indeed, unlike other Christians, Mormons seem to believe that all humankind is born already saved by the grace of Christ (Moro. 8: 12; that is why little children are alive in Christ) and that only our own sins (A of F 1: 2), if we reach the age of accountability, are a stumbling block. In fact, Mormons believe we lived with God before we were born. We already had everything other Christians are striving for and we chose to give it up! Why?
To Know God: Deification as Salvation
Because Mormons believe there is something greater than living with God: Knowing Him! “And this is life eternal, that they might know thee the only true God, and Jesus Christ, whom thou hast sent.” (John 3:17)
But what does it mean to know God? What is the ultimate way to know something? If I read a book about how to do brain surgery, I may understand exactly how to do it, but I don’t “know how to do it.” For me to know brain surgery, I have to internalize it.
Likewise, the ultimate way to know a person is to be like them. To know God as fully as possible one must love Him so much and wish to be like He is so much that he/she starts to act like Him, until our character and God’s character converge into one. 
“Beloved, now are we the sons of God, and it doth not yet appear what we shall be: but we know that, when he shall appear, we shall be like him; for we shall see him as he is.” (1 John 3:2)
“…have ye spiritually been born of God? Have ye received his image in your countenances? Have ye experienced this mighty change in your hearts?” (Alma 5:14)
When we know God that completely, God holds nothing back from us; we have become like He is. This is the Mormon doctrine of Deification and it is also the Mormon concept of salvation. The fullness of salvation is to know God so completely you are like He is. Living forever, even living forever with God, is secondary to Knowing God.
Have you ever thought about what this scripture really means? “Blessed are they which do hunger and thirst after righteousness: for they shall be filled.” (Matt 5:6) What does it mean to hunger and thirst after righteousness? It means you aren’t righteous but you wish you were so badly that it’s like a hunger inside of you. How is such a hunger filled? Jesus isn’t herein promising us avoidance of an inevitable @#!*% , he’s promising us righteousness!
No wonder he adds “Be ye therefore perfect, even as your Father which is in heaven is perfect.” (Matt 5:48) This isn’t a statement made by Christ to cause us to despair of our own righteousness and thus call upon the grace of Christ, this is a statement of the reality of what God’s grace can do to us. Filled indeed!
That is the significance of the Mormon concept of baptism being a covenant relationship with God. (Mosiah 5:5) We promise God our willingness: “they are willing to take upon them the name of thy Son, and always remember him, and keep his commandments which he hath given them.” (Moroni 4:3)
God is promising us grace in return, but not the Protestant concept of grace as a way of removing sins, though that is true too. This grace, or more properly “graciousness,” of God is that He will help us in our desire to be like He is. He will allow us to “always have his Spirit” (Moroni 4:3) with us as a constant companion now and forever until we attain to the promised blessing: To help us be like He is “that [we] may be one, even as [Christ and the Father] are one.” (John 17: 11, 21-22)
Obedience vs. Grace
But if salvation is forming a certain type of character rather than a trip to heaven, then we have solved another mystery of the ages: why “obedience” and “works” can neither merit salvation, nor can salvation happen in their absence.
If salvation is to have a certain type of character that acts in a certain type of way, then salvation is being the type of person that is obedient to God’s commandments. Our “works” aren’t how we obtain salvation, they are what we are trying to obtain itself!
No wonder Jesus warns us “Therefore… do not sound a trumpet before thee, as the hypocrites do in the synagogues and in the streets, that they may have glory of men. Verily I say unto you, They have their reward.” (Matt. 6: 2, 5, 16) How could a good act done for the wrong reason affect our character? It can’t! But affect to our character is the only thing that matters! Our “works” by themselves mean nothing to God nor us. But how that “work” affected our character is the very salvation we seek.
 For those Christians that believe a fall from grace is not possible, the official answer is that a person that goes out and commits unrepentant sin never really accepted Christ in the first place. The wording is different, but the end result is exactly the same. All else is word games.
 Ammon Rye pointed out that in Alma 24:11 (http://scriptures.lds.org/en/alma/24/11#11) The Book of Mormon defines “all we can do” as repentance: “And now behold, my brethren, since it has been all that we could do, (as we were the most lost of all mankind) to repent of all our sins.” There is actually a division amongst Born Again Christians between those that believe in “Lordship” vs. “No Lordship.” That is to say, some Christians believe one can accept Christ as savior but not as Lord and be savd while others believe you have to accept both. My statement that Born Again Christians, in principle, agree with 2 Nephi 25:23 is referring to “Lordship” Christians, which are the vast majority.
 An obvious difference I skipped over is belief in priesthood authority. But for this article, I’m concentrating on the doctrinal/theological differences.
 Variants I am aware of on how Protestant’s believe one accepts Christ are a) whether or not one has power on their own to accept Christ (i.e. has free will) or if God has to empower you to do so, b) whether you have to literally accept Christ or simply accepting God’s grace in any religion is equivalent to accepting Christ, c) whether or not one can accept Christ after death. “a” is the most common dividing point with “b” and “c” representing only minority views.
 Isn’t accepting Christ still a “work”? Calvinistic Christians reject free will in large part because they believe there is no work we can do to save ourselves. Arminians get around this objection by claiming that it was by grace that we have free will. Either way, God played a role in our acceptance of Him. I do not see the Mormon view as much different than the Arminian view on this one particular point. (It’s very different overall.) Mormons believe God allowed us freedom of choice.
 One Born Again Christian friend defined this change from an unsaved state to a saved state as being a transaction whereby the sinner accepts Christ and Jesus, at the point in time, pays for their sins. This friend, being Calvinistic, believes that is why a person can never fall from grace, because the transaction of grace has already taken place.
 One sizeable difference between Calvinistic vs. Arminian Christians is over if a fall from grace is possible due to your sins. Arminians often affirm that one’s sins can cause a fall from grace. Calvinists believe your sins cannot cause a fall from grace, but they hedge a bit on this by proclaiming that anyone that commits a serious sin, such a murder or adultery, had not really accept Jesus in the first place or else the grace of Christ would have kept them from committing such a sin.
 For Mormons, I use the word “obedience” instead of “works” because I believe it more correctly captures the Mormon concept of the importance of our choices and actions.
 I think a good way to think of this is in terms of “idol worship.” Lest you think I’m being sacrilegious when I say this, bear in mind that an “idol” is something that stands in the place that is rightfully God’s. Thus “idol worship” is to treat something else the way only God should be treated. When we “idol worship” a celebrity we dress up like him (or her), talk like him, learn about him, and emulate his life. To use a play on words, if we “idol worship” God, we are doing that which is correct.