There are some good websites that help you choose a dog.
Edit: just checked my bookmarks, and they're all dead URLs, or I would have linked them.
Everyone has their favorites. Border Collies and other herding dogs are really a great thing for some people. I for one can't stand them. WAY too much exercise needs for me.
I have owned Beagles, Bassetts, french bulldog, several chihuahuas, two pits, irish wolfhound, and a few other assorted mutts. You need to find the right mixture of size and slobber. The bigger they are, they are usually less needful of exercise, but they tend to do all the normal dog things with the same fervor regardless of size. They will all want to sit in your lap. Great if it's a Yorkie, not so much if it's a Dane. They all slobber to some extent. A chihuahua will drool wee little drops. A St. Bernard will ooze 5 gallons of mucus-like slime every time you crinkle a potato chip bag. It just depends on how much dog you can tolerate.
I am a strong believer in several things when it comes to dogs and choosing a companion that will make you happy.
1) Don't get a puppy. Puppies are cute and adorable and trip over their own feet making you laugh. A) the honeymoon will soon be over and the cuteness gives way to real life. B) I don't support the random proliferation of bringing new dogs into the world when there are so many homeless animals being put to sleep or living a horrible existence in a shelter. C) You can't tell what the disposition of a puppy will be when it reaches adulthood. My Bassett puppy began life like any normal adorable dog, but kinda turned into a douche as an adult.
2) Don't get a pure-bred or pedigreed dog unless you want to put up with health problems. If you plan on dipping your feet into showing dogs, then yes, get an AKC registered boutique dog. Dog breeds have been inbred and force-bred to hone specific phenotypes for human amusement. Many breeds have specific health problems that plague their kind. Unless you want to bring a dog into the world with the specific knowledge that they may live a horrifically painful life and/or you'll be saddled with intense vet bills to help it, get a mutt. At least if you get a dog that looks and seems like 100% [insert breed], an AKC registered dog means that its lineage can be verified several generations back, which sounds good, but it isn't. It means that there is a high likelihood that the genetic troubles known to that breed have been titrated, distilled, and concentrated. If you get a German Shepherd-ish dog without the fancy title, it has a much lower chance of hip dysplasia and crippling pain than one that has been bred purely with other verified Shepherd stock. The AKC has its heart in the right place, but generally, they serve (in my opinion) as a revenue/advertising stream at the expense of the health and proliferation of boutique animals that serve little or no purpose other than looking pretty on some ESPN off-season show.
3) If you meet a dog, it will act along a spectrum of responses to meeting you. They are pretty telling. A) won't come to you, runs, hides, barks, quivers. This is the canine equivalent of paranoid schizophrenia with PTSD. Pass. You'll never enjoy having friends over for dinner again. Every stimulus will be a debilitating, crippling, traumatizing experience for the dog. They won't be happy, and you will be miserable. A rare number end up (just like some humans) snapping when they have just bloody had enough of being the fearful goth/emo kid that gets picked on. B) excited to meet you, but tucks tail, pees, or slinks over and instantly turns over to expose their belly with their mouth mostly closed. This is the equivalent of a doormat. Spineless, afraid, Omega. They will have trouble integrating into life unless it is monotonous and routine. If they could talk, they would say "h- h- have you seen my stapler?" A rare number of dogs like this end up fine because you can work to build their confidence. C) excited to meet you, tail wags, inquisitive sniffs and licks, maybe a little belly while the tail is still wagging and mouth open. This is the winner. Well adjusted, confident, but cautious. Any dog that greets with confidence and a willingness to show submission is usually a winner. They are the Tony Robbins' of the dog world. It doesn't matter the situation, they are there to please you, and in the process it pleases themselves. D) excited to meet you, jumps up, strong licking, maybe a bit mouthy. Pass. This is the equivalent of that person at a party that won't shut up, every story they have is better than yours, and their last experience on a yacht with a famous person just HAS to be told. They are alpha. You will never win, and in the process of trying to win, you'll just be making their lives miserable. Dogs aren't like people in that they can't learn that their behaviors are causing their own unhappiness. All they know is that their instinctive brain told them to eat the peas in the trash can, and no amount of scolding, beating, or berating will un-do that instinct. At best, you can berate the behavior out of them, but you can't ever teach them the reason why they shouldn't have that instinct. All you will be able to do is make their lives miserable in an attempt to make them conform to YOUR learned behaviors.
If you have a treat, you have a wonderful tool to help you as well. First, it will tell you how food-driven they are. Highly food-driven dogs can be as annoying as the selfish kid. Once they know you have a treat, how do they react? Do they try to nudge it out of your hand like they'll starve without it? Do they sit and look back and forth between your face and your hand? Then, once you give it to them, do they have a gentle mouth, or does half of your hand go down their throat? I think you can derive which of those things is the preferable trait.
There is no real advice I can give you on breeds since any breed can fall into any of those categories. Size does matter though. I had a chihuahua that was a borderline D, but she was so small that any time she was a jerk, it was just cute. You're going to threaten me with a mouth that won't even wrap around my finger? That's adorable.
Chihuahuas and some other smaller breeds can seem to possess more than one personality type. The chihuahua I just mentioned was kind of a jerk, but at the first sign of discipline, she was a complete B.
The Pit I currently have is a total C. She is amazing. Happy, calm to the point of sedate, yet eager to run and play. She has single-handedly taught me that dogs are far more intelligent than we give them credit for. I swear she can communicate better than my ex wife. She knows she's not allowed on the couch without the blanket covering the cushions. She will straight up walk over to the couch, look at the blanket on the floor, then the couch, then me. If I don't notice, she'll make a slight verbalization, then repeat the three things. If she wants to go outside, she looks at me, then the door. She's brilliant.