First, decide what you want your dog for. Is it going to be a companion, a friend for kids, a guard dog, etc.? Do you want it to be attention craving (and thus more "loving") or fairly independent? Can you handle the strength of a larger dog if it becomes adamant about running away or attacking something, or the stupidity of most smaller breeds? Do you mind long hair and shedding?
Once you answer all of those questions to yourself, go on the dozens of dog breed info sites around the net and research. Figure out what fits your ideal description and read up on how well they do with kids, families, other dogs, whether they need a large yard or constant grooming, whether they can handle the elements (within reason) or need to be kept in constantly, etc. Remember that EVERY dog is different (we have a Golden Retriever right now that's far more hyper than our Lab or previous Siberian Husky ever was), so be sure to spend plenty of time with the dog / puppy before making a purchase or adopting.
If I had to pick any one breed for first time dog owners, it'd be a Golden Retriever. Labs are great too, but they tend to be a bit more hyper and can run into weight problems more easily. First time owners should especially avoid the highly independent or possibly aggressive breeds like German Shepherds, Siberian Huskies, Pitbulls, etc. While every dog is different and their temperment highly depends on their training, care, and conditions, this is a good guideline on what NOT to get if you don't know what the f%$# you're doing:
http://en.wikipedia.org/wiki/List_of_fatal_dog_attacks_in_the_United_States (note that there are a few oddities, as expected, such as Goldens or Labs on the list).