1) logo should be design in 2-3 colors and you have to check it with black and white print also. so in case if you have to print it in b-w in future, it should be looks good.
START in black and white. Think for every color you have, you add a plate, or a Pantone matching charge. I'm sure the OP knows what Pantones are, right?
2) icon must represent your company nature and its work. also it is going to become your company icon and people going to recognized your company only seeing its icon. so it should be clear and conceptual.
Yeah, good thing they're not selling underwear. Is your personal logo a person at a computer wearing a lightbulb t-shirt?
AroundTheFur, read PrintDriver's response, do what he suggests re: defining your hypothetical company, then sit down with paper and pencil and sketch 100 or so ideas. Do not jump onto the computer each...