Also remember, if you do miss something there will always be another sale. Summer and winter are practically gurantees, Halloween, Autumn, there are always more Steam Sales.
Also, typically the sale price of something during a daily deal or Flash Sale is the best price that particular title will have all sale. For example, Skyrim last sale was 33% off the entire sale, then went 50% off for a daily deal. Games are on a smaller sale for the entire duration, and then may get a bigger sale for a daily deal or flash sale. If the game you want is not on daily deal or flash sale, wait until the last day. The regular sale price will still be in effect and you always have the chance for it to go on daily deal.