When designing a new logo for customers, I like to create a flexible brand that will work on many applications but still be recognizable in different formats.
A layout of what will look good on a responsive website (with phone view) and what will look good on a business card or even a truck or van door can be entirely different.
Think ahead to all applications - it will save you headaches in the future. For instance, if you are a restaurant and you serve drinks in a clear plastic cup, you want that logo to be visible on the cup as well as the signage out front on your sign. So think of colors, visability and READABILITY.
Also remember that you are building a brand and it is something that you will have to live with for a while, so don't get to "cutsey" with icons. Starting out it may seem kind of "fun" but later on as a reputable company, it will lose it's appeal.
Whoever designs your logo, remember you will want to know the names of the fonts used. You will also want...