First off, check if you should be buying at all at this point. Obviously it seems like the logical thing, but it can be a millstone around your neck if it's not right for you at the moment. There are numerous sites which will help you weigh it up financially, like this. Think about how long you want to stay in your first place and if you can afford to buy somewhere you're going to want to make a long term home. How long you want to stay can certainly affect how good a deal it is.

If and when you do go for a house, make sure to check a number of things. If you're renting at the moment, think about the things your landlord will take care of - that safety net is no longer there.

Be sure to think about the following:

Electrics: is the wiring okay? Do the switches work, etc.

Roof: is there any discernible damage from the outside?

Damp: check the outside walls for signs of damp. If you can, get access to the attic as well. Look for dark patches and condensation.

Insulation / double glazing: is the house at all energy efficient? Your bills will be higher if you're spewing heat out of the windows. Remember heat travels up, so is there loft insulation?

Space: is there enough of it for future developments? If you're single, what if you get a live-in partner, etc.? You don't want to have to move based on smallish changes of circumstance.

Parking / surroundings: do you like the area? Are there reasonable amenities nearby? Is there somewhere for you to park with little hassle? What about visitors? Is the house on a flood plain etc.? Speak to the neighbours - do they have any gripes?

Internet: are you in a reasonable area for internet? Is there a provider monopoly locally? Can you get fast enough speeds? This one may seem frivilous, but it may be quite annoying in time to come.

I'm sure my list is non-exhaustive, but it should act as a good starting point and help get in the right mindset.