You need a I 20 that has been signed by your advisor. The signature is valid upto 1 year so basically if you had a new I 20 signed 11 months ago you're good. Not a bad idea to get  letter of good standing from the advisor as well. tickets, money to spend in Nepal, visa to return back after youre broke in Nepal and presents to all your family, thats all you need. Also couple of ipods, laptops and iphones if you want to sell them there and have money to spend in Nepal.