Google pay per click is the fastest real time traffic out there. You can also loose your investment in the blink of an eye if you don't know what you are doing. Of course you will need to study which keywords are converting for you and shut those down that don't. But here is one under utilized tip that only maverick, masters, and great students use. NEGATIVE keywords by the bucket load.

Do an all time search query report on your campaign and you will see what people typed in to actually see the campaign. If you look at it, you will see many of those search queries were not appropriate for your campaign. It was not the traffic you were looking for, and cost you money. So look at those reports and write down your list of words you don't want. An example would be "illegal", anyone searching for illegal ways to do anything is not the type of customer you want. So you would add that word as a negative. Your negative list should be huge, and you want to add to it all the time. Your negative keyword list will be way longer then your keyword list in your adgroup.This one tip will save you a ton of money and actually bring you the traffic you really want.