I'm a woo-er. I can't help it. When I find something that is amazing, I must tell others about it. So check this out and be convinced on how awesome this tool is.
When you have anything in mind over $20 that you want to buy, but you are not in a super rush to buy this item this website is fantastic.
(okay most ridiculous website name ever.) (But stay with me, it's good.)
You go to Amazon.com, find said item, copy the link of that items page.
Then go to camelcamelcamel.com and paste the link of the item into their search engine.
This website creates a beautiful graph (I'm from a family of math nerds...yes beautiful graph) of all the price changes on amazon in the last year (sometimes less if the item has not been on the market that long. Sometimes more like example below goes back since 2012) You can then see if the price listed is a price you really want to pay.
Let's say the price isn't right for you yet. You can set up a very simple "Price Watch." You enter your desired price and then they email you when that price is hit. (They also don't send you unnecessary emails that clutter up your inbox which I appreciate greatly.)
For example, last spring I knew I wanted to get my nephew Ticket To Ride for his birthday. I put in a price watch for when the price went below $32. I then got an email one day (on April 5th according to the beautiful graph) where the price went down to $29.99. Woot for me!