It is always a good idea, in advance of signing a lease, to ask about the pet policy. Ask a lot of questions, such as...

Will my landlord allow me to have a dog?
Is there a weight limit?
Is there a pet deposit or fee?
Will your landlord allow more than one pet?

Assuming you get the OK from your landlord... now for the serious questions...

What size and breed dog would be good for our family?
If you have children.. do the children want a dog and will they take an active role in caring for a new family member?
Is the yard fenced? If not who will walk a new dog 3 or 4 times a day?

It's important that the activity level and temperament of dog matches the home. So many dogs are surrendered to shelters because the family gets a cute little puppy but then the puppy grows up and the family is not prepared to put the time and effort that is required to train and care for a dog.

Adopting a pet is not an impulse decision... do your research and make sure you are ready for the commitment.