How much do you bid per click with adwords when you try to build your list?

Since this is your first list, it's a tough question to answer. For more established players, the answer would be "how much can you afford to bid and still make money?"

When we used to run lead-gen ads for a business opportunity, the sweet spot was bidding to stay in the #5-#8 position.

The top spots get more clicks, but a bigger proportion of them are curiosity clicks, particularly if the organic results are uninspiring.

Another tip that runs counter to conventional advice is to avoid the word "free" in your ad. Again, your raw number of clicks may suffer, but the quality should be higher.

The last tip I can offer you at this point is that a large negative words list is your friend. You can use it to keep your ad off of marginally relevant and irrelevant pages, where you could end up paying for wasted clicks.

For example, during the holidays I run a campaign promoting the box set of the series "Friends". After a couple of days, I was getting people looking for "Thomas & Friends", a kiddie show. Adding 'Thomas' to my neg list cured that.