1. NEVER TALK TO THIS GUY
Unless they are some guru mechanic, don't talk to anyone working in a bike store who does not shave their legs. Rather, find someone in a bike store who lives and breathes this stuff and who suffers from cyclists' Toruette's, meaning they can't help blurting out everything they know about carbon soles when all you asked for were socks. Through racing and buying socks and gloves, I've made friends with a few such dudes and they're golden. Think of them as sometimes verbose personal tutors, there to impart whatever knowledge you need to extract from their encyclopaedic cycle-buff minds. Let their love be infectious. Repay them by buying all those things you want NOW from their shop, and letting them price match on big stuff.
2. BUT ALSO SHOP WITH A PEN AND PAPER IN HAND
Hang out in shops to glean info. Find a shop you hate, where you would never buy anything, purely on principle, where guys with hairy legs ask if they can help (which they can't) and just use their change rooms! Find out, for example, what size Santini nicks you wear, before you go home and check out the prices online. Try shoes out for size. Take bikes for test rides, but never negotiate prices—at least not on their turf.
3. DO YOUR ACTUAL BUYING FROM HOME
Like arguing over the price of pop-corn once you are there at the movies, talking turkey in a bike store is useless. Sit on the computer and the phone and play them all off. In Australia, Bikeexchange.com.au gives you a toll free line to every bike store in the country, and thousands of listing like this one for bikes which stores are desperate to clear. Also Cellbikes have great value homebrand bikes on their front page, that are useful for comparing prices and haggling.
Rather than spending over 2K for the individual components I need for a top-secret prototype I have in development, I asked around and learned Mongoose were clearing 2008 models of a bike that just happened to come with everything I need: 36 spoke 29er mtb wheels, hydraulic disc brakes, and internal hub gears. In the end I found a bike store in Canberra willing to do me one of these for $1100 then I phoned Greyhound to go pick it up. By telling it was a parcel of "sporting goods"—never say it's a "bike"— I got the freight down to $84 door to door. So here is a picture of my "donor bike", that I'll ride around for fun while my prototype frame is being welded up, then strip it and sell this frame on ebay. btw Mongoose do some good value bikes with named components right the way through.