Orm, I hope you consider a rescue dog - they come in all shapes and sizes, and ages and colours! And you can get cat/other animal friendly ones too. A reputable rescue will carefully assess the dog before homing it - they will make sure the dog is vet checked, neutered, chipped and wormed, and will provide behavioural support if needed, advice as well as a permanent place of safety should you at any time change your mind/your circumstances change. Many rescue dogs are family pets who are rehomed through no fault of their own - common reasons are divorce, family breakup, emigration, house move, change in working arrangements which are nothing to do with the dog and everything to do with the owners circumstances.
Silent has made some very good points about checking out a local vet (you will be a regular customer, so it makes sense to find one who is close by), and also finding out about training classes - these are a must whether you have a pup or an adult dog. Depending on the type of dog you get, you might also want to think about other dog related activities - there's flyball, obedience, CaniX and lots of others. Have a think about where you will be walking the dog - it makes it very much easier if you've got good parks/open spaces near you. Other things to do in preparation - make sure garden is secure and think about arrangements for when you are not at home/have a day out/go on holiday - check out local dog walkers/kennels etc.
For anyone getting a dog, I'd also recommend a serious think about the finances - you need to budget for food, insurance ( a must, in my view) annual vaccinations, worming, minor vet visits/ailments, grooming/clipping for some breeds, holiday arrangements (good kennels cost a fortune at peak times), bed, leads, collars
and possibly coats. Depending on travel arrangements, your car will need to be dog proofed - possibly a crate, dog guard or seat belt arrangement/harness depending on size.
It's also essential that every ADULT in the household is signed up and committed to the idea. Although children can be keen/nag interminably - it is not them who pay the vets bill, or generally them who walk the dog on cold, dark February mornings. And if an adult is living in the house and not keen on the idea, there is a very much greater likelihood of the situation breaking down. To be fair, it's important to consider the downsides. They can be very messy, smelly, expensive, will be a tie for up to fifteen years, long after your kids have left home, may well trash your furniture/decor, leave hair everywhere, be a terrible tie, and finally will break your heart into a million pieces when they die.
Knowing all this though, I'm completely addicted/besotted, but just thought it would be fair to mention this. 