Use the leanest meat you can find, Many Mexican markets will have Asada or Milanesa cuts. Fat on jerky will make it spoil quickly. Use a good marinade to flavor, I like to introduce liquid smoke about the last hour of the marinade. I did find it's almost always cheaper to buy it than to make it, but it is fun to come up with your own flavors. And hide it, it will disappear fast!
"When I was younger, I could remember anything, whether it had happened or not." - Mark Twain