PPC advertising is a dynamic auction system, so your competitors’ bids are likely changing all the time. There are many factors that are in a constant state of flux.
Let me suggest to you that your objective should not be a particular CPC, instead, it should be maximizing profit. You should be trying to find the Max CPC bid that generates the maximum profit per month.
Once you have enough data to establish a reasonably accurate conversion rate for a particular keyword you will be able to adjust your bid to reach maximum profit. Calculate your average EPC (Earnings-Per-Click) and set your maximum bid at about 70% of the EPC. Then begin adjusting the bid up in small increments, and if your total profit increases continue increasing the bid until the profits begin to decline, then go back to the most profitable bid. Be sure that you wait until you have adequate data, for a reasonably accurate calculation, before making each incremental adjustment.
Tools like Spyfu are highly inaccurate, I wouldn’t recommend using that data for setting your initial bids.
Here’s a tip to help you select your initial bid level for your keywords. Set a high bid initially, using the data from the AdWords Keyword Tool, along with a reasonable daily budget limit. Something you can afford to lose as an investment to gather your initial set of data.
At the end of the first day, adjust the bid down on keywords that received impressions, but not so low that it drops off the first page. You can use the AdWords Editor to download the estimated minimum bid for first-page placement of your ads after you have generated some impressions for the keyword.
Once you have enough data to calculate conversion rates on most of your keywords, you need to increase the daily budget limits significantly, as the daily budget limit is a poor way to manage your ad program budgets. Instead, you will manage your budget based on optimizing profits, not some arbitrary number.
Also do not bid on broad match keywords initially, stick to exact match keywords during the first few days, then add in your phrase match keywords, using a lower range of bids than used for your exact match keywords.
