So general consensus:
Wait for the daily deal. Do not bite on the week-long sales unless it's crazy CRAZY low (rare occurence) because it might go cheaper during a daily.
If possible, add a set amount of funds to your Steam Wallet so that you don't have to deal with rejecting banks and bad credit cards. If that's not possible, try to make one purchase a day with 3-4 games in the list instead of 4 difference purchases. This way, it's less likely that your bank will freak out at the sudden money spent.
Before jumping to a sale, quickly check in here. Someone will probably have a reccomendation on the price or the game itself. If a pack that's normally $100 is going for $10, obviously go for it, it's usually a Valve glitch.
Activision probably won't lower their games anymore then 5-10%.
Valve loves to basically give away Source games so expect low prices.
EA prices are high compared to before,
because of their move to Origin. Look for deals on there before making a move on Steam for EA games only.