When designing a logo it is important to make sure that the logo can function in multiple environments. This means that your logo design should still look good when its very small or very large. Sometimes we forget this because we get so caught up in the design process. Now I’m not saying complicated and detailed logos are forbidden, there is just a time and a place for certain types of designs.
Feel free to ask your clients what they plan on doing with the logo so you know ahead of time where the design is going to appear. Its good to get into the habit of stepping back for a moment and testing to see if the logo reproduces well when your shrink or enlarge it. Also be sure to test the logo in different colors and in black and white.
Remember its ok to break the rules, but its better to be able to follow the rules first before you start breaking them. Below is an example of a logo that reproduces well in multiple instances: NBC Logo