Nothing is more important to the outcome of a successful bid than an excellent opportunity/business capture effort. There are three areas in particular that are critical to a successful capture effort and bid, these are: cost, business intelligence and customer bias.
I frequently hear people say "we lost on price - we need to figure out some way to lower our rates". Winning the cost proposal is a function of capture. Let me say this again, winning the cost proposal is a function of business capture! You must have a high assurance that you can win on cost BEFORE the bid decision is made. Don't be fooled by "best value" determinations, you must always assume that key competitors will have solid past performance and write as good of a technical solution as you will.....meaning that cost may be the critical deciding factor.
Here is the bottom line, if you don't know your top two or three competitors, how they are perceived by the customer, their key strengths and weaknesses from customer perspective, then it would be better NOT to make a bid decision.
While I would never understate the importance of writing an innovative technical solution that clearly and succinctly addresses the requirements, understanding customer bias is equally, and possibly in some cases more, important. While I would never question the integrity of a source selection board, the facts are that the vast majority of people make buying decisions at the unconscious level. Your ability to identify key customer/source selection committee "care abouts, biases and hot buttons" during the capture effort will help you "connect" to the selection committee in your proposal. Remember that a proposal is a communications document - you are trying to connect to the reader/reviewer.
While proposal preparation is critical, you will either win or lose the contract based on the strength and completeness of you opportunity/business capture efforts. If you have done a great capture job, you'll have all the right ingredients for a winning proposal. Now how simple is that?

