The main stuff I'd say is wait for sales and don't just check Steam for sales but other stores, though make sure you are getting the game as a Steam key if you buy it elsewhere (most stores will tell you this on the page).
isthereanydeal.com is a great resources. It compiles sale prices and history from multiple stores for pretty much any game. It also lets you import you Steam wishlist and will let send you notifications when a game on your list goes on sale if you so choose (Steam does this as well but only for their store; ITAD can do it for all stores).
To go along with that, I highly recommend the Enhanced Steam web browser plugin created by
fellow CAG Neogaffer

Jshackles.
http://www.enhancedsteam.com/
It will grab price history from isthereanydeal to tell you what the current lowest price and historical lowest price of a game is as well as if it has been in any bundles.
If you're interested in Indie Games you can also check out the
CAG Steam etc Buy/Sell/Trade Thread (aka The Cess Pool). It's mostly people selling off extra keys from Indie Bundles but if you're completely new to Steam you probably don't have any of those games and may be able to get them really cheap there.
This place is a good place to hang out and chat but if you're in a hurry and want a really quick at a glance for mostly PC game deals (with a tiny smattering of some console deals thrown in; sort of the reverse of CAG) then
https://www.reddit.com/r/GameDeals/new/ is a good place to just quickly browse.
Sorry guys the people at the place annoy me too but just keepin it real that if you just want to check quickly for deals it's an easier format and you don't have to go into the comments and read their inane nonsense anyway.