The foremost scripture that the Evangelicals use in defense of their doctrine of salvation by grace alone is from the Apostle Paul, in Ephesians 2:8-9: "For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast." First and foremost, we must understand that the Apostle Paul was speaking to his Gentile converts (members of the Church not of Jewish ancestry). A majority of the disputes of Paul's day were that the Jewish converts still believed in the necessity of the Law of Moses and it's tenants of obeying strictly the Law - or doing works, in other words. However, Paul was not speaking of salvation by works. He was saying that the Law of Moses was fulfilled and that the Atonement of Christ ultimately saves through His grace. Nephi put it more plainly in the Book of Mormon. Said he, "For we labor diligently to write, to persuade our children, and also our brethren, to believe in Christ, and to be reconciled to God; for we know that it is by grace that we are saved, after all we can do (2 Nephi 25:23)." As Jesus said in John 3:5, "Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God", we all must be baptized to gain entrance to the gate of salvation. Nephi says again in 2 Nephi 31:17, "Wherefore, do the things which I have told you I have seen that your Lord and your Redeemer should do; for, for this cause have they been shown unto me, that ye might know the gate by which ye should enter. For the gate by which ye should enter is repentance and baptism by water; and then cometh a remission of your sins by fire and by the Holy Ghost." Thus we see that by works (baptism) and grace (saved after all we can do) are we saved.
Another example is the woman taken in adultery. After our Lord had answered the Scribes and Pharisees, insomuch that they were convicted of their guilt, they departed. The Lord than said to the woman "Woman, where are those thine accusers? hath no man condemned thee? She said, No man, Lord. And Jesus said unto her, Neither do I condemn thee: go, and sin no more (John 8:10-11)." Here we read Jesus saying, "go, and sin no more." He did not say "I forgive you", because the woman had not yet merited His forgiveness; He expected her to work at becoming better, as He previously said, "Be ye therefore perfect, even as your Father which is in heaven is perfect. (Matt 5:48)" Because Jesus is the Son of God, His grace was to make up the difference in the woman's repentance - and finally grant forgiveness. Son Ahmen hath said in revelation, "For I the Lord cannot look upon sin with the least degree of allowance; Nevertheless, he that repents and does the commandments of the Lord shall be forgiven (D&C 1:31-32)".
Lastly, it is my personal opinion that the greatest scripture that describes the means of grace and works working together is Ether 12:27: "And if men come unto me I will show unto them their weakness. I give unto men weakness that they may be humble; and my grace is sufficient for all men that humble themselves before me; for if they humble themselves before me, and have faith in me, then will I make wake things become strong unto them." This also applies to salvation - that if we do all we can to keep the commandments of the Lord, He will strengthen us to do so, and thus land our souls in His kingdom. What I have spoken is true, and defy anyone to show me differently. In the name of Jesus Christ, Amen.