When checking on web site links many people raise the question is the other site linked to a bad neighbourhood ? A good way to check to see if the other site is worth linking to is via the page rank of that site. Sites which have no page rank are either not that established or could be questionable in terms of their own links. Also, do not be afraid to trust your intuition if the site does not feel right to you then chances are that it would be bad to link to.
Linking to promote your website is best done in such a way that those links will be informative to your customers.