I've made quite a bit of jerky. I experimented with all kinds of marinades and dry rubs and cures. While I usually prefer making things like this from scratch, I could never find anything I liked as much as Hi Mtn Jerky original seasoning and cure (stay away from the flavored ones though). For about $7 you get enough to do 15 pounds of meat. In the Minneapolis area, it's available at Cub Foods stores. Online you can find it at http://www.himtnjerky.com/
Something else that I use that comes in quite handy is a jerky board and knife. Basically, it's a wood board with a 1/4 inch lip on one side and 3/8 inch lip on the other. The knife is very sharp and very thin. You lay the meat in the board and run the knife along the top and gives you perfectly even cuts of meat. Works like a charm. You can find it at http://www.butcher-packer.com/pg_jerky_board.htm
I always use top round steak because it's very lean and not as expensive as other lean cuts. You want to avoid fatty meats for jerky so just keep that in mind with whatever you use. Trim it well before smoking it. Cure it, cut it to uniform strips, and throw it on the smoker. Many people like their jerky really tough and chewy. I prefer mine more tender so I always cut the strips across the grain of the meat.