You'll need a jack (the one that comes with your car or truck works), two jackstands, hand tools, oil and an oil filter. You'll also need a drain pan to catch the oil that comes out. Gloves come in handy so your hands don't get gunked up.

If you have a car or low truck, you'll need to pick the front end off the ground. Never get under a car that's supported by a jack, so you'll need to put it on the jackstands. Make sure the engine has cooled so you don't get burned by hot oil.

Look under the car for the oil pan. It'll be directly under the engine (and not on the transmission) with a hex head bolt for the drain. Slide your drain pan under the bolt and remove it to let the oil out. Remove the filler cap to let the oil drain faster.

While the oil is draining, locate the oil filter and remove it. Some oil will come out from the oil filter mount as well, so make sure to catch it in the drain pan. Rub a bit of oil with your finger on the new oil filter's rubber gasket to make sure it seals nicely, then screw the new filter on.

If your car has a weirdly shaped oil pan or you had to put the car up at an angle to reach the drain bolt, you may have to return the car to the ground to let the oil completely drain. Make sure not to crush the drain pan like I did the first time I changed my own oil.

Once the oil has finished draining, replace the oil drain bolt and begin pouring oil in the engine. Return the car to the ground for this to make sure you get an accurate reading on the oil level in the next step. If you returned the car to the ground earlier, you may be able to reach the drain plug with it on the ground. Make sure not to over-tighten the drain bolt, or you may strip it. Hand tight is good enough. If you have a new gasket for the drain bolt, replace the gasket before replacing the bolt.

After you've poured 3 or 4 quarts into the oil filler, remove the dipstick, wipe it off, and replace it. Remove it again and check the oil level. Keep adding oil until the level on the stick reads that the engine has ample oil.

Start the engine and let it run for about 30 seconds (making sure you don't see any leaks!). Recheck the oil level and add oil as necessary, as some of it will be pulled from the pan into the oiling system and the engine will need topping off to make sure it has a good supply of oil.

After this, you're done! You can dispose of waste oil at your local auto parts store.