Making Money From Online Fiction – I’ve Done It, So Can You – Novelr has some great advice from someone whose done it and made a profit essentially giving away a free product. He has some really great notes on the effectiveness of Paypal buttons as well, very scientifically mapped out-
I’ve tried PayPal buttons in various places around my sites, and this is what I know: a link in the right sidebar gets clicked 0.21% of the time. The same button in the left sidebar gets clicked 0.01% of the time. The link can be “below the fold” (not visible when the page first loads), but too far down and your click rate drops to zero. Putting the link inline almost never works (0.002%), and at the start of the text, it’s utterly useless (0%). Placing a link at the bottom of a chapter or page often works, but you need to be careful that the reader feels a sense of closure when they see that link. Cliffhangers and wrap-ups work nicely (1.1%), but if you’re just arbitrarily cutting the text mid-stream, those links never get clicked. And sometimes you get hate mail.