Twenty-some-odd years ago I spent two years in Ohio as an LDS missionary. They were a great two years. I met so many wonderful people.
In December, my son will be doing the same thing, in a different place: the Philippines.
Over the past two decades, I've thought a lot about my experience and what I could have done better. Here's what I told my son a couple of weeks ago... (knowing that he was going on his mission, but not knowing where the assignment would be)
The next two years will be an opportunity for you to _learn_ how to serve and help other people. Probably, at no other time in your life, will you have such an opportunity to focus on something quite this completely. Use the time well. Your job is NOT to convert people to the LDS Church. Your job is to be a disciple of Jesus Christ, to love people, serve them, and help them. Don't ever get caught up in how many people join the Church or how many discussions you give, or anything like that. Those things are easy to measure, but they don't mean anything.
If you want to measure something, keep track of the number of times you get a sincere "Thank you" from someone.
I've spent time in the Philippines. There will be no end to the good he can do. What a great learning experience this will be.