Thought I'd bump this thread up and get it going again as 2014 parents/friends get ready to send mail to the incoming basics. Christcorp's post towards the beginning has lots of good info.
One of the biggest things for parents to remember is each squadron is different in what they allow/confiscate/do with letters. Your child will let you know if something is a no-no when they write to you. Our son wanted us to send jokes - his cadre liked hearing jokes at mealtime. If it was a good joke the meal went a lot better.
BUT -- write them often. I wrote my son every day - not long letters but everyday. Eventually I started typing them so I could remember what I wrote the day before and not repeat myself. I'd also cut and paste some ESPN articles on his favorite teams -- they got through to him; newspaper clippings were confiscated. I'd number the back of the envelope so he'd know which letter was written before another as he sometimes got 2-3 letters at one time.
They don't get to the mail room everyday during BCT - they have to march everywhere and marching the squad or flight to the mail room doesn't always fit in. But he knew there would be a letter there for him anytime he went. Even now as a 3* he tell me "it was SO good to get those letters during BCT; they really helped me".
Be prepared to get the this place is horrible letter; encourage them as much as you can. Tell them others feel the same way; others are messing up all the little details too; you're not alone in how you feel. Oh, and should you get a phone call saying they want to leave - listen to them, but ask them a few questions -- like, what is their plan if they come home; was today a good day or bad day - they shouldn't make those type decisions on bad days - each day brings different things and they need to take it one day at a time.
There is a yahoo group out there for fellow 2014 parents.
http://dir.groups.yahoo.com/group/usafa2014parents/?v=1&t=directory&ch=web&pub=groups&sec=dir&slk=9
All classes have yahoo groups and they share great info with one another. You might want to join to check it out. WebGuy on the AOG site will have forums too - they are good for info and commiseration also
Good luck -- enjoy this wild, fun ride. And thank you to your children for answering the call to serve our nation.