Whether you are planning on building an in house Bid Management Tool or simply conducing a manual analysis to manage your PPC Bids, Data Storage & Filtering is the foundation to any bid management strategy. Historical Data and performance of your PPC Campaigns is important because:

Historical Data should be used to make data driven decisions [...]

There are a lot of Bid Management Tools in the market - and it can be daunting to decide which one to use. I prepared a list of Questions you can ask them in order to determine their fit with your business model:
Engine Functionality

Does it work with three major Search Engines, Google AdWords, Yahoo Search [...]