1 lb Beef (I used a shoulder cut, I think. It was lean and on sale)
1 Bottle Teriyaki sauce
You can make you're own sauce, dry rubs, etc. I tried two other flavors besides the teriyaki one, but didn't really like either one of them. Although, almost any sauce you like, will likely taste good on beef jerky. I used a homemake worcestershire based sauce that Forrest really liked, and I recommend finding one you like!
Slice beef into strips.
You can buy it in strips sometimes, or have the butcher do it. If you're opting to slice it yourself, try and cut at an angle, and slightly off of the grain. See bottom note for more details.
Mix in marinade, and marinate overnight, or at least 8 hours, in the fridge. I put mine in a ziplock bag, and squeezed most of the air out.
After marinating, lay beef flat on a baking sheet, and place in oven, preheated to 170-200º, whichever is the lowest temperature your oven will allow.
Bake 6-8 hours, turning once or twice after 3-4 hours.
Your home will smell amazing! Forrest LOVED it when he walked in the door and had such an awesome snack.
Here's what I mean about 'slightly off the grain'. Look at your beef and figure out which way the fibers are going. If you line your knife up with it, and cut into the beef, you'll be going with the grain. If you look at the slice, you'll see long lines going up and down. Now, if you turn your knife 90º and cut, you'll be going against the grain. So, if the grain is going left to right, and your blade is going up and down, it's against the grain. If you cut it, you'll see a bunch of sections, rather than long lines.
Now - how to cut slightly against the grain. Line your knife up with the grain. Now, turn your knife (or beef) slightly, like 5-10º. If you look closely at my pictures, you'll be able to see what it should look like.