For some indication, our wedding tog was £350 for the day, but then we got ass raped on prints and an album to a total cost of around £2500. He wanted £1800 for CD of images.
12 months after he sent an email offering the DVD of images for £300, he was politely told no.
I have just started myself, and charge £400 for the day + DVD of images. Doing albums/prints are on top.
One of the best togs on the east cost starts his basic package on £1500 for 2 togs for the day (well 1/2 a day).
You need to decide what you can afford and pick the tog who's work you like the best and that you get on with. Lots of togs have letters after their name too, these indicate which professional bodies they are part of. Check them out as some you simply pay a yearly fee and you are in, others you actually have to pass an entrance board who judge your work. The latter is much more desirable.
Ideally you want one that provides edited photos on a DVD and gives you printing rights for them, but also, if you require can do an album, although you could do your own photobook instead. Photobooks are a hell of a lot cheaper, and are the type of thing you can leave on your coffee table. If it gets ruined, its cheap enough to replace
Make sure they have insurance for at least public liability, not only does this cover any of your guests, you and your wedding, many venues insist on it now as does your own wedding insurance.
make sure the tog you meet is also the tog that will come to your wedding, some outsource. And ask them what plans they've got in case they can't make it on the day.
That's all I can think of off the top of my head.
EDIT: One other thing, many venues have photographers that they recommend. Now, I am in 2 minds about this. Obviously if they know the venue, they know all the places and angles to take the shots from that many new togs won't know. On the bad side, they've shot there so many times your photos will look like everyone else's that got married there and they are just banging out the same generic poses.
This is what our tog was like, had shot there 100's of times. Same generic photos, in fact, you could line all the different weddings up and they all have the same shots.