Hi ADbeat,
You could do some web searches for "melody" "writing". Some general, timeless rules are:
1) Most good melodies usually consist of stepwise movement, but with enough skips for interest.
2) The melody should have a climax, a high point (intervalwise).
3) There should be some consistency. This means that you should see if you can find little patterns that sound good, and string variations of them together.
4) While you are trying to make the melody consistent as a whole, there must be enough variety to give it life.
For example, while repeated notes and patterns are good up to a point, try to use as many notes in the scale as you can. Vary the rhythms in a pattern, enough so that they seem related, but so they keep the listener guessing.
5) efd753 made two good points.
A) First, learn harmony. Once again, you can search the web or go to your local library.
B) Second, if you don't already play an instrument, start now! Theory without hearing and practicing, won't get you very far. And playing an instrument without absorbing all that's been learned in the last 700 hears will cut you off from attaining you highest creative potential!
The links below are just to get you started ...
http://guitar.about.com/od/writingthemusic/
http://www.musesmuse.com/rblb-4.html
http://www.berkleeshares.com/songwriting__arranging/writing_chorus_
-Mike