Writing an LDS missionary who you met on his mission?

[Mindy]

I'm in college, in a province outside my own. I met this missionary who ironically happens to be from the same province as me, we live 2 hours away from each other and we also ironically have a mutual friend. He's home in 2 months. One month before me. My friend here married a guy who she met while on his mission, and she's my age (under 21). She wrote letters to this missionary. I had asked this missionary if he has facebook, and he did, so his sister accepted my friend request for him. Although I have 2 months until I can chat with him online and instantly, I want to write some snail mail letters. I'll only get about 5 in, but I'd like to get together with him after his mission. As we live SO close. He recently got transferred, because it's the only mission in the world that has one Canadian city in a USA mission, he had to go back south due to when he gets released. I'm not sure what to write... I've never written a letter to a missionary before, as I didn't know him until I moved, and he got transferred. I had applied to go back home in the fall, and he applied to the same city (different school), and one 5 hours south. I've been told to ask about hobbies, interests, goals. But this is a first letter... and it's only been 2 weeks, and it will be 3 by the time he get it. I want to keep it supportive and encouraging, but I don't know how. I've gotten advice from my dad and my friend, but I still feel lost! I've prayed about him, and snail mail seems to be a good idea. I've been a member my whole life, so I should know this, but I've never really been on a date... even though I'm an adult. Help!!!
Also... how long should I wait until after his mission to try and get together? I don't want to be that girl who grabs the guy really quickly, I want it to be honest. I know it's different for every guy... but I don't want to talk about it too soon, even though he'd have a month to be getting out of the mission mind. I don't want to be forceful. He's a really nice guy and he was the only missionary who complimented me on prayers and testimonies. Does that mean anything or am I just thinking things? I am so confused! I'm not experienced with dating or talking to guys... in a "I want to get to know you" sense, even though he and I talked easily.
The mission is 2 years! Btw of no dating... no thinking about dating, it sounds harsh, but it has such an spiritual impact.