A good logo design is a part of brand building, and sometimes the main aspect of building a brand. A good logo design must be appealing to the eyes. It must not be an inappropriate image.
The designing of the logo must be such that it leaves a lasting impression on the target audience. Such that the next time they see the logo they can recognise it or at least place where they had seen the logo last.
A logo must always be simple and easy to figure out. If a logo is cluttered with too many elements or has a text that is difficult to read or understand, people will not always take efforts to read or remember it.
The colors in a logo must be attractive
The theme of the logo must be in sync with the product or at least the target audience.