Okay, so my dad is making me hit the gym with him this summer, but he wants me to do pushups. No one has even really taught me how to do a pushup though. I mean, i can do like 5 then I'm already spent. How do I do a pushup properly?

lie on your stomach all flat out
lean ony our palms about shoulder width
extend them till fully extended
get on your toes at the other end
keep your torso tight and in line with your ass and legs and back
press up and down staying tight, with your arms

everyone starts at fewer than a dozen at some point in their life, unless they managed to avoid them entirely while putting up big bench press numbers (and even that translates into fewer push-ups than you might guess). the way to get better is to do them every other day, or every day, and always try to do at least one more than the day before.

Do them controlled as well, you don't get much out of doing pushups, but might as well maximize what you can.

2 seconds up, 4 seconds down. When you're doing the "up" part of the pushup, a nice controlled 2 seconds is good. Control the "down" part so it takes you a good 4 seconds to come down.

Keep doing pushups like that, as Throttle said, 1 more than the day before is always good.

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If I were you, I'd set a repetitions goal as well, for instance, if your goal is to do 15 pushups. Do 15, then once you get to 15, put some weight on your back and go for 15 again. A bag of rice or something that weights 5-10lbs is a good start.

http://en.wikipedia.org/wiki/Push_up

It has a .gif of a guy doing them.

If you're having problems do the girly pushups (on your knees) until you build up the needed strength and endurance.

Then you can move to regular pushups, then to one arm, then to weighed... etc.