One word - testimonials...
If someone I know and respect has something good to say about a product that I think I might need....consider that bought
And oh, the seller...who's selling it?
I have groups of people I buy stuff from..
the gurus - not always the easiest to decide whether to buy or not
people i have bought from before - becomes a no brainer at this point especially if you have testimonials from others I trust in the market
Unknown people - people I've never heard of means I probably dont buy..especially in the IM niche (unless you supply me with testimonials...) And, I stay away from pages with paypal "proofs"..just turns me off