RESPONSE TO THE ORIGINAL QUESTION: Trade secrets
I work in LBS #1 which does high-volume business of high-mid to into level bikes. EVERYTHING IS ALREADY MARKED BELOW MSRP. You want to ask for last years models (marked off several hundred dollars), Demo bikes (these probably aren't in "like new" condition), or bikes with scratches.
In our store, this is pretty much the only way to get a bike knocked down. Keep in mind profit margin is pretty thin on bikes. Accessories are slightly more profitable, but the entire business runs on pretty slim margins.
As for accessories, most shops will have a policy of 10-15% off accessories with the purchase of a bike. be sure to ask about this up front instead of waiting until you're at the counter paying. Secondly, dont expect a salesperson to be able to negotiate pricing, inevitably they will have to ask a manager.
The best way of approaching this to get the best value for your money is to know how much you're willing to spend and tell the salesperson up front. That way we can work with you to find where you want to splurge and where you want to skimp. Time and time again I see people who dont want to disclose their price range and we end up spending more than expected on the bike then skipping computers, helmets, lights, shoes, etc; and I personally believe this lowers their bicycling experience.
Disclaimer: I realize other stores have different policies.
I hope this helps answer your questions. I'll answer anything else if you want to know.