This means selecting programs that naturally complement the subject matter of your site and that will therefore be of interest and relevance to your site visitors. Keeping the need for synergy uppermost in mind, look for quality programs first and foremost. The last thing you want to waste your time, money and reputation on is a shoddy product or service. There are just too many quality programs out there to settle for anything less. Any reputable company will have full contact details readily available so do your research.
References Look for testimonials and references from other affiliates.
If the company you're interested is not forthcoming when it comes to putting you in touch with other affiliates, move on. This shows that the company is serious about its business. Watch out for exclusivity clauses and other restraints. Some affiliate agreements will require that you not promote competing businesses' products and services. This is not to say you should avoid such agreements.