Ah oh, a few more Rizla pro posts and my comments are going to seem worthless.
First I would like to state I'm nowhere near as knowledgeable as Rizla, or even close in digital and multimedia art. I study ancient art, mostly renaissance but I've delved in contemporary art. I've never really done anything in Photoshop because I love the freedom of a brush or a pencil. Now that you've got that in your mind here are my advice on logos:
Take a look at these(
http://www.artgraphics.ru/identity/best2006eng.html), and before even you look for similarities I'll point out the major ones:
Repetition- Repeat SOMETHING, it has been shown that the human brain looks for patterns and tries to sort randomness into patterns, the most famous case being stars, it helps their memory especially if there is one presented to them.
Color Scheme- Don't blast them with colors, one or two color compositions are the best. Two color go with complementary colors, one color use only gray and white for shade and light, once again this adds to the memory factor Rizla mentioned.
Negative space- Unlike signatures, where overuse of negative space means less attention on the focal, use the negative space wisely. Because you're not using an eclectic range of colors and renders the negative space is vital for telling everything you can to your viewer and providing another message.
Text- More important than EVER in logo. You have about 5 seconds to present a large amount of information in a tiny package. Which means everything will be scrutinized for a long time rather than glossing over an entire signature, or a wallpaper, or bigger if you will. Text->Product, the text alone should give the viewer enough of an idea about your company, or at least the mood you want the company to present.
That's all for now, I keep thinking I forgot something, I may come back if I recall later.