There are many things to think about when choosing a new member of the family.
Puppy or adult dog?
If you decide to get a puppy have a good think about what breed you would like and look into what reputable breeders are near you.
If you are thinking about having a cross breed (pedigree dog crossed with another) or mongrel (where the parents are crossbreeds), try and find out what they are crossed with, this will give you a good idea of what size they might grow to and a rough idea of what their temperament might be like. Research into exercise requirements, feeding requirements and any common health issues.
There is a lot of hard work that goes into to caring and training for a puppy so be prepared for some hard work!
Rescuing an adult dog can be very rewarding for both new owner and the dog. However rescue dogs may come with some problems which will require some time, patience and possibly some further training. If you have gone to a rescue kennels then ask their advice to see if the dog you like would be suitable for you and your family.
You will need to think about weather you would like to have a female or a male. If they have been neutered (if they are from a rescue centre they should have been already)
Owning a pet can be expensive, so have a look into pet insurance for peace of mind.