could you be more specify on what keywords you want? it depends .. some say that a position 4-6 is good for them .. and i personally think that bidding too much to stay on the first position is not a wise idea... just my 2 cent i personally have a few ads - only bidding on min $0.05 per click
Pay as much as it takes to get into position 8/9 (within reason of course) I find if are on the front page you will get the traffic, and it will be the best traffic....second page is okay if the price is two high on the first page but you will be paying for probably at least twice as much for each conversion......I mean two times as many people will only look at your site then move on as opposed to those who click on first page ads. If you are on page three or more, forget it, anyone clicking on ads down there are only looking around. You might jag a sale every now and again but if people are clicking on your ad the chances of them buying from you are very small. A big point to consider is the copy in your ad, it's got to be good enough to attract people but don't overdo it by saying things like free and they get to your site and find it's not free, you just wasted your money as they will move on.