My Craftsman Mower model 536.270282 won't start, I've replaced the spark plug, battery and have new gas in it as well. It try's to start but won't "spark" and I can smell the gas so the choke seems to work as well and have looked at the manual also to see if I missed something, I'm at my wit's end and the grass is getting tall!

If its turning over but not kicking on check the magneto... Google "small engine magneto repair" or something similar for more help. On mine all I had to do was sand a bit of rust off and adjust the clearance (about the width of a business card) and it has run like a top ever since. One spot to get started: http://science.howstuffworks.com/question375.htm