Decide why you want a dog.
Dogs can be good companions. They come in all sizes and activity levels. Some do best with one person; others love a big household.
If you are planning to get a dog to put on a chain to protect your house and yard, think about a security system instead. Putting a dog on a chain is both cruel and dangerous. In July of 2014, the city of Hereford made it illegal to tether or chain a dog in an unfenced yard.
Decide if you can afford a dog.
A dog requires food. It doesn’t have to be the most expensive food but the cheapest may not provide sufficient nutrition for good health. (Food scraps do not provide everything a dog needs and may even include foods that can make a dog sick.) They need vaccinations to protect their health and sometimes the people they live with. Sometimes they need Veterinarian care and medications. A dog needs a collar and an ID tag. A leash is required when a dog is outside it’s yard. Chew toys are good to discourage a dog chewing up shoes etc. Depending on the dog, training may be necessary to teach manners.
If you think a dog would enrich your life, then start thinking about size, activity level, type, and finally breeds. Read everything you can find about the breeds you are interested in. Read the bad as well as the good points about a breed. Breeds are more than looks. Quite often it is about the job the breed was developed to do over many, many generations.