A good rule of thumb for a logo is, when you are designing it, shrink it down to 1"x1". Thats a pretty common size for a logo, and a lot of people create them at a large size, then when they get scaled down that far they lose a ton of definition and suddenly start to look really cluttered. It'll help to refine your design to consider what it'd look like if it were that small, and you'll start to see what kinds of things should be defined, or simplified, etc.