Some estate agent's details have plans attached, some don't. I find that they're really useful for recalling what it looked like, what the flow of the house is like. I have taken to marking them up with the big un-movable items, like cookers plumbing points etc, so I can look at them again later.
If you like the house, make sure you go and look at the area and its outside at different times of day. sure, it was lovely at 11:00 on a sunday morning, but the place is completely clogged with school traffic at 9:00 weekdays and is a cut through from the pub at chucking out time - none of which you'd know if you only went round the once.
open cupboards, to check storage space, look behind large or numerous pictures (you don't know what horrors might be hidden by a strategic picture) look behind doors and curtains. sellers aren't all stupid and will try to disguise any obvious flaws.
Look at the ceiling to get an idea of how much space there is in a room, especially one that's cluttered. the ceiling is usually freer than the floor, so can be a better guide to the space avaliable.
Most sellers will have a value they want to achive, but will also have a sliding scale of what they will accept depending on the situation of the person offering (I know we do!). A first time buyer is a good thing, as it means you are the bottom of the chain. Always ask what the chain is (if there is one as yet) as that can have an impact on the complexity - a short chain should go through easier than a long one, as there are fewer parties involved and fewer sets of people to sort out everything.
Especially if it's an older house, or in need of some work, as a local electrican and gas specialist to have a look at these for you. This will tell you if everything is in working order and if it is to current standard or not - this can have a big impact on how much work may be required if you decide to do it up.
Be prepared to look at anything, even if you think you wont like it, you never know, it might be a diamond.
Know you budget and stick to it - don't be tempted by the one that's just out of reach!
We're selling our first house at the moment and it's nothing like as much fun as buying the first one was! Good luck.