In Alma 17, we read that as Alma and Amulek continued teaching and preaching, they ran across the sons of Mosiah, who were returning from their mission to the Lamanites. Verse 2 says, Alma did rejoice exceedingly to see his brethren; and what added more to his joy, they were still his brethren in the Lord.

Then Mormon gives us a formula, telling us what these men had done to retain their testimonies.
1) They had searched the scriptures diligently
2) They had given themselves to much prayer
3) They had given themselves to much fasting.

I had originally thought that was the end of the list. It's a great list, with the essential elements. But today I discovered in verse 4 another step that's also very important.
4) They had been teaching the word of God for 14 years.

It's very important to gain our own testimonies and to keep those testimonies bright through study, fasting and prayer. But it's also essential to share our testimonies with others, teaching our families or church classes or through missionary work. Teaching reinforces, reminds and strengthens those things that we learn.