First of all are you sending International or only in the USA ?
If you are sending only in the USA you only need to send a SASE (Self Addressed Stamped Envelope) Which pretty much is a envelope with your address on it and put USA stamps to cover postage to send it back to you if you are unsure how many stamps you need check UPS or your nearest postal office. If you are sending Overseas you will need to do the same send a SASE inside the other envelope but the thing is USA stamps will not work for e.g. you want to send a letter to someone in England you will need to put a SASE in the envelope you are sending in but on the SASE you will need UK stamps to cover postage back from the UK. Buying stamps from another country would be cheaper then using IRC ( International Reply Coupons ) I'm not sure how much they cost where you are but where i am they cost like $5.00 so i find it much easier buying USA stamps considering i am from Australia. Makes sense ?

I live in the U.S. , so do I just send a good amount of stamps with the picture or dvd i'm sending? or do I ask the post office person for a "reply coupon" ??

second question: I know UPS would be more expensive, but is it ok to use UPS to send autograph requests? Do they have reply coupons too?