I use the following:
¼ cup soy sauce
1 tbsp Worcestershire sauce
¼ tsp cayenne pepper
¼ tsp garlic powder
1 tsp seasoned salt (Lowry's, Tony Chachere's, etc).
t tsp liquid smoke

I think you could probably omit the liquid smoke and it would still be fine, although it gives it a nice hickory taste.

Also, if you don't have a dehydrator, note that the oven works just fine too. Put it on the very lowest temperature (175-200), lay the jerky out on a rack set over a pan to catch the drips, and bake it for 3-4 hours until it's fully dried.

You really will be amazed just how much better homemade jerky is than store-bought -- the quality of the meat makes a HUGE difference! I just wish beef prices would go down...