I just found the excellent Shy Person’s Guide to Calling Representatives on tumblr. It’s very reassuring for those of us who hate phone calls or worry that calling over VOIP will cause problems.
The big take-home is this – you don’t need to be eloquent, and you don’t need to convince them of anything. You need to them to mark down that you called and what you stance was.
By the way, I’ve been told that the calls with the most impact go to the representative’s home district, not DC. So find that number.