Ohh, I'm a jerky pro!
I wait til I find london broil steaks on sale at the local market (anything less than $1.99 is acceptable). I usually buy around 12-20 lbs, and freeze them all overnight. I wake up the next day, set them out for about 2 hours on the counter and let them thaw just ever-so-slight, then slice them. Much easier to slice them thin (1/4") when they are frozen still.
I make my marinade on the stove. Typically a mix of soy, teriayki, Worcestershire sauce, liquid smoke, tobasco, red pepper flakes, pepper, brown sugar, maple syrup, etc. Heat til the sugar disolves, and then pour over the meat in a large container. Toss it all in the frige for 24 hours. The next day I pull it all out, and dry off excess marinade with paper towels. I then season them with a mix of black pepper and garlic powder.
At this point you're ready to dry the meat. I always toss the meat in my smoker for 2 hours with a sweet wood like cherry, pecan, or apple. This makes an enormous difference in the overall taste. Do this at a very very low temperature! I then take it off and toss it in my cheapo dehydrator for about 10 hours or so.