The best thing I can think of is URL expanders which can check for redirects and whatnot and tells you what they are. Google 'em, there's a ton out there.
Just right-click the link and see if the URL shows anything suspicious. If its been shortened with a service like up4eva.co.uk or bit.ly etc then use unshortner.com to unshorten it first!
Well, if you don't want to buy via affiliate link, there is a simple way like this: use anonymous model browsing of Google chrome (by press Ctrl+Shift+N) --> your browsing will not be recorded into cookies and thus, affiliate link didn't work anymore. Try it! good luck!