One of the things that always amazes me is when someone gets a dog as an impulse buy. There has been no consideration of what the actual needs of the dog are going to be and if you can fulfill them. This is one of the reasons (not the only) that our animal shelters are swamped. Now don't get me wrong I tend to be a little impulsive myself at times. And it does not mean if you impulsively get a dog you are to fail. 
Some other issues I run into constantly are: someone does not understand (they thought they did) how much time, money, etc, goes into a dog; a household is divided on whether or not the dog was wanted to start with; and no consideration is made based on your current home. So here is a basic check list of things to ask yourself if you think you want to get a dog.
1. How much extra money do I have in my budget for a dog's needs? 
(Shortlist: food, water, dishes, kennel and/or bed, toys, training,  poo bags, treats, vaccines, unexpected vet visits, boarding costs) 
2. How much time can I give the dog each day?
 (the answer to this question might help you sort out if you want a puppy, an adult dog, or a cat) Be specific with the time frame, for example friday I can dedicate 2 pm-2:30 and then 5pm to 6pm. It is important you do this so rather than saying Oh I could spend 12 hours week giving it my complete attention you actually look at when you can give it your complete attention. I would say if you cannot give it one on one attention for at least an hour a day 80 percent of the time don't do it. 
3. How much am I home?
 (If you are not going to be home a lot you need to add in the thought of taking the dog to a dog day care during the day or if the dog can go with you where you are at. Dog's should not be left on their own for extended periods of time. That is how you get destruct-o dog.)
4. IF you live with other people what do they think of you getting a dog? 
I have known families that got a dog but Dad didn't want it. Guess what, Dad did everything he could to get rid of it. (add mom in to that instead of dad and I have seen it too.) Roommates need to be very careful with this because their other roommate(s) might be allergic or scared of dogs. I love dogs but sometimes you need to put the people around first. 
5. Where are you currently living?
consider your neighborhood, HOA, Are you in home, apartment, condo? Do you own or do you rent? IF YOU RENT you NEED to clear it with your landlord before you even start looking for a dog. (there will be a post on that topic later) 
6. What breed(s) are you considering? 
Even if you plan on adopting you need to figure that out. Do your research on the breeds make sure you find ones that work with your situation. (there will be a post on this topic later as well) Make a list of breeds that will not work and DO NOT get a dog with one of those breeds in it. 
7. Are there any policies in place in  your neighborhood, HOA, Insurance, City, County, State, Complex, etc that would dictate whether you could have a dog or what kind of dog you can have?
Always double check this before you starting to look for a dog. You will be surprised how many of these policies there are. Some areas are  no dog, some have breed or weight restrictions, and some have very set rules for the process of getting a dog. Be aware
8. Are you willing to commit to the dog for the remainder of its life? 
This means you do not get rid of the dog for any reason including health problems or because you want to move. If you want to move you need to find a place you can go with your dog. You have no business looking at places that would require you to get rid of your dog. 

 9. REMEMBER THE DOG IS NOT A PIECE OF FURNITURE OR A COMMODITY. Dogs have the same emotional maturity of a three to six year old child. If you would not do something to a young child you should not be doing it to a dog (there are obviously some exceptions to this but it is a good general rule

Now these questions do not include everything you may need to consider before getting a dog, but they are an excellent starting point. RESEARCH you answers thoroughly. 

I love dogs. I love having dogs. But what breaks my heart is when dogs are brought into circumstances where they cannot be taken care of or is neglected. It kills me when someone complains how big an inconvenience their dog is. They obviously did not think it through before they got one. Many of the people I work with have thought it through and are wonderful with their dogs. But I have found they do not view their dogs as burdens and they are happy and so their dog can be happy.