depends on ur site and content
"GOOD" keywords are keywords that are popular both on your site, and in Google. For instance, good keywords for a site called "company name Web Hosting", keywords would be "hosting" and the type of hosting it offers *free, dedicated, shared, etc.* The name of the company is a bad choice because its likely no one would search for the words of your company, unless it is something general.
You also want to make sure that the keywords appear often on your site. This is called keyword density. Keyword density is the percentage of keywords on your site. For example, if your site has 1000 words, and you use the word "hosting" five times, then the keyword density is 0.5%. You want a keyword density of around 5-10%.