Nearly three years have passed since President Thomas S. Monson of The Church of Jesus Christ of Latter-day Saints announced the historic change to the church’s missionary program. It’s become known colloquially as the “age change” — meaning that worthy young men can serve at the age of 18 instead of 19 and after graduating from high school. Young women can serve at 19 instead of 21.

While serving as a young man — and later teaching for a short time at the Mission Training Center in Provo, and even now having Mormon missionaries into my home as often as possible and working with them at every opportunity — I’ve learned a few things about the differences between happy, successful missionaries and the unpleasant alternatives.

I call them my 11 can’t-miss tips for successful missionaries.

Be obedient — period
Sister Anaseini Kolo of Lotofoa, Ha'Apai, (Anaseini Kolo)

1. Be obedient — period. Following mission rules brings blessings you cannot fathom until you are immersed in obedience. Learn the rules and follow them.

Don't judge
Elder Braden Birch of Farmington, Utah. (Matt Birch)

2. Don’t judge. At times, you will feel tempted to judge other missionaries and their efforts. Remember, your skills and natural abilities may be different than those you serve with. Their best effort doesn’t need to be good enough for you; it needs to be good enough for the Lord.

Be obedient every minute of every day
Missionaries from the Utah Provo Mission. (Jason Wright)

3. Be obedient every minute of every day. You are unlikely to meet returned missionaries who were obedient but still regret their missions. But you will certainly encounter others who were never consistently obedient and never found the promised success and happiness. Being obedient doesn't mean you won't have difficult days, but it does mean more much success and happiness than otherwise.

Serve your companions
Elder Brerick Hullinger and Elder Dylan Holden prepare to baptize Tyshaun Spencer.

4. Serve your companions. Iron their shirts, make their beds and shine their shoes. If you’re blessed to be assigned a more challenging personality or someone who’s struggling, serve them even more.

Be obedient — even in the small things
Elder Colton Utley of St. George, Utah, and his companion. (Tricia Utley)

5. Be obedient — even in the small things. Obedience is the only frequency that the Spirit operates in. Be sure you’re dialed in every time you walk out your front door to share the gospel.

Give praise
Sister Stephanie Wright and Paige Sears. (Ann Wright)

6. Give praise. Tell your companions, especially the challenging ones, that you think they're great missionaries and, eventually, they will be. At some point you will inevitably be assigned the companion with the “reputation.” Let them know you’ve only heard terrific things about them and offer a clean slate. When your mission is complete, be the one who says every single companion he had was amazing.

Be obedient
Elder Jared Bellon, left, and Elder Zachary Shorts. (Julie Bellon)

7. Be obedient. You will make mistakes and grow better each day at effectively teaching the gospel. But while you can't be perfect in all things, you can be perfectly obedient.

Sister Susana Zubeldia, left, and Sister Lindsay Sorensen (Rick Sorensen)

8. Love. Love those you teach with all your heart, even the ones who ultimately reject the message. You will plant seeds that may not be harvested for months or years by others who will come after. But you'll harvest some that were planted by missionaries now home, married and gray.

Exercise faith
Sister Jessica Wells, middle, stands with President and Sister Lima. (Kevin Wells)

9. Exercise faith that obedience leads to greater success. If you have faith in this principle, you will see it unfold in miraculous ways.

Love each and every day
A group of missionaries point out their mission destinations on a map. (Audrey Lusk)

10. Love each and every day. Young missionaries only get this opportunity to serve 24/7. Leave nothing behind and don't regret a single day.

Be yourself
Elder Kyle Hodges and Elder Vinicius Machado. (Sharon Hodges)

11. Be yourself! Smile! Laugh! Have fun! Sometimes elders and sisters think that obedience and the black name tag means you’re required to shelf your personality and become ultra serious. The Lord doesn’t want us to be different people — he wants us to be better versions of ourselves.