In Alma 27:18, we read,
"Now was not this exceeding joy? Behold, this is joy which none receiveth save it be the truly penitent and humble seeker of happiness"
So in order to have exceeding joy, the scripture says we must:
1) Be truly penitent : Penitence as defined in the dictionary is "Feeling or showing sorrow and regret for having done wrong; repentance" One step in being truly happy, then, is to repent. In a 2006 general conference address, Marcus B Nash said, "Each of us needs to repent to some degree or another. To repent means to make the real changes in your life the Savior desires you to make for your happiness. Repentance is the great enabling principle of the gospel: when your faith in the Lord causes personal change, such action on your part, as Helaman states, “bringeth [you] unto the power of the Redeemer, unto the salvation of [your] souls” (Helaman 5:11)."
2) Be humble : We can't search for happiness out of pride or selfishness. We have to be humble and always grateful unto the Lord. In the Doctrine and Covenants 1:28 we read, "And inasmuch as they were humble, they might be made strong."
3) Seek to find it : In Matthew 7:7-8,Christ says, "Ask and it shall be given you; seek and ye shall find; knock and it shall be opened unto you. For everyone that asketh, receiveth; and he that seeketh findeth; and to him that knocketh it shall be opened." True happiness won't just come to us. We have to strive to find it in it's fullness and it will be granted unto us.
So now that we know what it takes, what is this true happiness really like?
In Alma 27: 17, he writes, "Now the joy of Ammon was so great even that he was full; yea, he was swallowed up in the joy of his God, even to the exhausting of his strength; and he fell again to the earth."
We may not all fall to the earth, but I know that it is possible to be swallowed up in joy. I have found that when I do those things that I need to I have so much happiness in my life! The Lord really can bless you with more joy than I can even imagine. Isn't that such a great blessing? :)