It needs to be clean, crisp, related to the industry / business and look appealing on the eye. This means don't use sharp fluorescent colors. Think curves and smooth gradients. Also make sure its memorable and if you can... try and make it really clever. Like the FedEx arrow in their logo and the A to Z of the Amazon logo. Little clever ideas.
Start off with a mind map, note down everything you have in mind, possible clever tricks within the logo, colors etc.
You can get loads of inspiration from CSS galleries such as
www.creattica.com that might feed you with ideas. And also check out color palettes for the logo over at
http://www.colourlovers.com/
Hope this helps!