Yeah, a lot of schools do not have a letter service. I just made it very easy for them since my school did not have a service. Providing them with stamped letters that are already addressed is a good thing. I also made it clear that most schools were looking for the same information so they could really only write one letter on a word processor and only make minor changes as needed. I also made sure that I gave them all the info they could ever want . . . resume, dates of interactions we had, particular strengths and weaknesses in my application, traits about me that I felt he/she may have noticed, and of course instructions on who the letters need to be sent to. I found most profs were very good about it (and was told several times that it is their job to write LORs and that I should not feel bad about it . . . I was also told that it was so nice for me to make it easy on them). As for addresses, look on the schools' websites. Often those have an address for LORs to be sent to.