Recently I was speaking with an entrepreneur who was bragging about hiring a very expensive graphic designer to design a logo. The entrepreneur was spending a huge portion of his startup budget on just the logo. This is a very common and costly mistake!
A logo is your trademark. As a general guideline, it should be recognizable and unique. Anything else depends on your industry and target demographic. For instance, sometimes you will want your logo to obviously indicate the product or service you offer. Other times, you want it to be more subtle or just be something memorable. But your logo will never be the key driver of your business. Having a great logo or a catchy slogan will mean nothing if you provide a bad product or service. Similarly, having a decent logo will be good enough if you provide a great product or service.
In the case of a startup with very little seed capital, wasting money on an expensive logo is a bad investment. If you have a large amount of seed capital, then it does not affect you as much.