Most recipes are developed for microwaves with 800 to 1,200 watts. The higher the wattage, the faster things will cook, so if your microwave is super powerful, it will cook your food significantly faster.
Wet things microwave better than dry things do — generally, the wetter the better, and oil conducts better than water. Oatmeal is better than cereal; fish is better than meat. (Simply boiling water, however, is not recommended.) Wet-cooking techniques like braising, poaching and steaming are your best bets.
Cover foods while you’re microwaving them so they don’t dry out. Check your plastic wrap to make sure it’s microwave safe, and poke a slit in it with a paring knife to vent slightly (and prevent steam burns).
Stir foods often — most microwave ovens have hot spots. Unlike with a regular oven, where you lose heat every time you open the door, you’re totally allowed (actually, required) to check your food regularly in the microwave.
Food generally won’t brown in the microwave — only a couple exceptions, like nuts, seeds, coconut and bacon, have sufficient fat and moisture that will allow them to crisp up and darken. (Cover bacon with a paper towel to minimize spatters and cleanup.)
Avoid steam explosions by poking holes in hot dogs, sausages, potatoes — anything with a skin where steam can build up and force an escape in a hurry. And definitely don’t microwave whole eggs.
If a recipe tells you to let something stand for a while after it comes out of the microwave, listen to it; microwaved foods usually need to rest longer than conventionally cooked foods do because they’re usually more water heavy, and they retain more heat and continue to cook for longer.
Microwaves do differ pretty significantly, and getting used to each machine might require trial and error. If you’ve never cooked with a particular microwave, err on the side of shorter cook times; you can always add extra time on the end.
What not to microwave
A really remarkable array of foods, it turns out, will explode in the microwave. A short list:
Whole eggs (This is worth repeating. Really, don’t.)
Grapes and raisins (This is because plasma exists outside of science fiction contexts, and we are not sure what to do with this information now that we have it, but raisins are involved.)
Chocolate-hazelnut spread (Peanut butter is fine, but the fat content in this one makes it plenty sparky.)