Before checking your score on one of these sites, you can find out which credit score they will give you. (blog.readyforzero.com)
In fact, if a company checks your score for marketing purposes, without you asking for a loan or a credit line increase, it still won't affect your score. (bestratesin.com)
Credit scores range from 300 - 850, and you should make a point to check your score at least once, if not twice, a year. (credibly.com)