This is my standard recipe that I use for pretty much any gravy I make. This recipe was passed down from my mom (and possibly from her mom) and it's one of the first recipes my mom ever shared with me. It's also incredibly easy, which is a big plus. We use it every year on Thanksgiving with our turkey and every time we make roast beef.
1/2 cup flour
1 cup water
stock, or juice from cooking your meat
1 tbsp Kitchen Bouquet
Put your stock in a saucepan and then put your saucepan on a stove at medium heat. While you're waiting for it to warm up, mix the flour and water together in a drinking glass with a fork. Your mixture should be slightly thicker than milk. If not, add some more flour or water accordingly. Using the back of your fork (not the tines) begin stirring your gravy while pouring in the flour/water mixture. Keep stirring as the gravy begins to bubble and thicken. Once the gravy is thick enough for your taste turn off the burner and remove your pan from the heat. Stir in the kitchen bouquet, and voila, your gravy is complete!
My only complaint about this is that there it never lasts long enough, so consider adding some stock to the juices from your meat so that you have plenty of gravy!