Type of Logo (Textual/Iconic/Illustrative): Textual + Iconic (e.g. Yahoo with the Y!), or just Textual is fine too (e.g. Google). It doesn’t even necessarily need to have a lizard image.
Colour: Not more than 2 colours (excluding black / white)
Other Information :keep the textual unique but simple. The iconic logo should also be easy to draw, e.g. the Twitter’s bird or Yelp. The logo should be easy to reproduce on other marketing materials, e.g. stationeries, can be clearly identified on black and white print.
Some examples of clean and simple logo can be found at Yahoo!, eBay, AoL, TripAdvisor, Amazon, Slate, Skype
Very important to emphasis is to keep it look professional yet friendly, not casual and fun.