YIPPEEE! I got to mail my boxes today!
EHellDame already mentioned something I was going to suggest - use the Flat Rate boxes the USPS provides. I didn't have any, but I got some for my next mailing.
I had one box full of microwave food items - my troop has a microwave. And, another box full of other stuff - batteries, hand sanitizer, vitamins, antibiotic cream, paper products, pens, hard candy, and letters to various "Any Soldier".
I always get so excited when I send these boxes out. I keep wondering what it would be like to open the box and see what's inside. I hope the things I picked are helpful to the people I sent it to.
Even though I looked for bargains and got several "2 for 1" deals on things I got, I still spent more than I'd realized! I don't mind a bit! I get so excited buying stuff and trying to think of what I'd want if I were over there. You can spend a few dollars or hundreds of dollars. You can even just send a letter - they want those desperately. It's totally up to you as to how much you want to spend.
One thing you might consider, by the way, is to put another addressee on the Customs form - there's a place at the bottom of the form for what to do if the person you've sent it to is no longer there. Put "Deliver to Chaplain" in that spot. If your person is already gone by the time your package arrives, it'll at least get in the hands of someone who can still deliver the stuff to whoever is still there. Chaplains are great about doing things like that.
I want to do it again! I'm ready to pack up another box!