How do I Change oil 2003 ninja 250?

You first need to buy 2 or 3 quarts of 5w40 non-energy conserving oil and an oil filter, usually you can just ask the guys at napa and they can look up which one you need. First you drain the oil into a 3+ quart container, wait for about 15 min, put the plug and your new filter back in, then add 1.5 quarts, wait a little then check the side window while the bike is level (not on centerstand or kickstand). Keep adding until it goes up to about halfway up the glass. You should probably start it up then wait five minutes to make sure it is still half way up. Whenever you get back from a ride, you should visually check your oil, after five minutes it should be in the middle of the glass.