A logo should be:
A simple logo design created with line art with basic shapes including the company name is the most effective. Good logos use minimal colors (3-4 colors or fewer) no gradients, no more than four words, avoid very thin graphic elements. A logo needs to clearly communicate the business’s message.
An effective logo should be memorable and this is achieved by keeping the logo design simple and unique.
Will your logo still be effective in 10 or 20+ years?
A logo should be versatile to be used for web, print collateral, signage, and promotional items. For this reason, a logo should be designed in vector format, to ensure that it can be scaled to any size without sacrificing the quality and resolution of the logo. It should work with minimal colors to reduce costs when creating clothing, signage, and promotional items with your logo.
A logo should have the appropriate text and graphic elements to appeal to your target audience. For example, if you are designing a logo for a circus it would be appropriate to use a fun font & color scheme. You would not use a fun font if the logo was for an investment firm and your color would be more subdued.
These are just some simple tips to keep in mind if you are designing your own logo. Check out this interesting Forbes article for some additional info on logo design.
What Message Does Your Logo Convey? (Forbes)