Have been asked to contribute considering I work in a camera retailer, not really sure what to write so I'll just throw a bit of verbal diarrhea out
When someone comes in to buy a digital SLR, we (the collaborative retailer, rather than myself) can usually tell straight off if someone:
a) doesn't have a clue
b) has done their research, but still doesn't have a clue
c) knows what they want, and what to do with everything
For the a's and b's, we usually ask a price range. We do try and milk them for their money, so say for example you have a £300 price range, we'd see if we could sell you a £400 camera.
Usually people like the sound of Nikon and Canon, simply because you'd rather buy something you've heard of rather than something you haven't. That isn't to say Pentax, Olympus and Sony are rubbish cameras. Far from it.
Now, when we sell a camera, we don't get commission. I don't know how it is for other companies. What we DO get is incentives- for example, if we sell a particular camera one week, we'll get a bit of a bonus in our payslip.
This month we've been told to sell the D700. Anyone seriously looking at the D700 wouldn't spend the extra £100 to buy it instore, so we haven't sold any at all.
Now, going into a camera shop to look at cameras. Have an open mind, but generally, don't listen too much to the sales advisor. 50% of us know what they're talking about, 25% own a camera, 10% are passionate and knowledgeable about photography. You never know who you're going to get, so don't listen too intently to the drivel they come out with.
Hold the camera, try out the focusing, settings, menu system. If you want to be shown a feature on the camera, ask the advisor.
Now, if they're a good salesperson, they'll try and sell you extras - filters, cards, bags, tripods, lenses, flashguns, batteries, warranties, battery grips, ttl leads, lens clothes, you name it, they'll try and sell it.
Out of ALL of those items, the only thing you'll need is a card. If you buy your camera in-store, and just can't wait to use it, buy a card with it. If not, buy a card online. It's literally a third of the price.
I would recommend getting a case as well. But that's all you need. Find out what you want to use the camera for, and upgrade from there.
As far as the retailer goes, depending on the salesperson depends entirely on what you'll walk out with, if you literally have no idea what you want.
I am a Canon man, and I love the canon cameras. I know them inside out, I know the kit lineup, I know what you need, what they do well, what they don't do as well, what the competition is. I know a fair bit. And that is really evident in my sales.
As far as everyone else goes, I don't know.
One bit of advice I can give you. Try before you buy. If you intend on buying the camera, and the sales adviser gave you a good service and was friendly, consider spending the £30 extra buying it from the store. Perhaps that £30 was worth it so you didn't blindly buy the camera.
Don't really know what else to write. If I'm asked something, I'll stick it in here.