Louis Miller disappeared dear, after drawing out his cash ... -Mack The Knife

One sure fire way to spot a shark is to try and close out his sales page. Sharks won't let you go. Try to close a shark's page and you'll get the famous "BUT WAIT..." either through sound or a pop-up window.

This technique is a dead give away that you are dealing with a shark. Usually you will be offered a $10 discount on the already low price or a "friends and family" discount. Again common sense! Why are you suddenly their friend or worse yet their family? Some sharks don't know when to quit. I tried to close a shark's sales page once and kept getting the stupid wait box--they reverse the meaning of the quit and proceed buttons--and when I finally had cursed my way through 4 or 5 "But Wait" screens the make-millions-overnight product had gone from $77 to a mere $17 with only 3 packages left. This was beyond "friends and family"; I shuddered and left.

Rule # 2 : If you have ignored Rule #1, then try to close the sales page and see what happens. If you get any form of "Wait", you are dealing with a shark.