A WebmasterWorld thread discusses strategies about what you would do if you started advertising with a brand new keyword in Google AdWords. Are you compelled to pay a lot per click at first or start your bids low?
The responses vary greatly and it's interesting to gauge the strategy. Some people start a little higher:
I've always done it by starting about 50% higher than my max bid (so if my max bid is 30c, i'll start off with a 45c bid), but put a low campaign maximum. This way I can establish a click history so i'm not penalized right off the bat by having bids too low on historically high cpc rated keywords.
Others price it according to competition:
Here is what I do on a new site. I set a moderate price on my better keywords Not too high or low. Put a pretty good size daily budget on. Keep it on for 24 hours daily. When the high bidders have spent their budget or vacate their their normal time slot, you should be able to move up the page and garner some traffic. Conversion of course always depends on the site, content, the offer, etc.
What do you do when you have a brand new keyword? Personally, since we've implied that it's an existing campaign and we're merely adding a keyword, I would be compelled to use the max CPC and see how the ads perform with this keyword. Depending on the CTR, I will lower or raise the bid.
If you have anything to add, forum discussion continues at WebmasterWorld.