I recently walked Rosie, an adorable (adult) Beagle. She was very high-energy and just wanted to go, go, go. I'm certain I could've walked her for 8 hours and she still would've wanted more. Rosie was extremely interested in smelling everything, no matter how gross or how out-of-her-way the stinky item was. Rosie has a high prey drive, so she was able to instantly zero-in on squirrels and rats. Rosie was also trainable, but very stubborn. As soon as her nose was locked onto something, it was nearly impossible to break her keen focus unless I was waving a treat inches away from her nose. With treats, however, she was quick to respond to commands like "sit" and "paw".
Rosie, like many beagles, is also very smart and is able to quickly understand when she's faced with a problem, and how to solve those problems. For example, while we were walking, we took the stairs. However, next to the stairs was a wall-type barrier which remained the same level while the stairs were going downwards. When Rosie began to walk along the barrier, she quickly realized that the leash was not long enough, but that it was also too far to safely jump. Without my nudging her or luring her, she walked back the way she came and joined me down the stairs.
While Rosie can be stubborn at the most inopportune times, she can also be stubborn in the best ways: she is incredibly affectionate. If she wanted to lick my face, there was no stopping her. If she wanted my attention, she would rise up on her hind legs and put her front paws on my legs (and there was no teaching her otherwise).
Rosie did well with other dogs, but she mostly ignored other people, so I didn't have to worry about her jumping on them. Her positive and excited attitude, her high energy, and her intelligence would make her a good fit for older children and young adults looking to get a dog. They do need a lot of exercise as they were bred as hunting dogs, but they don't all need a lot of attention, and are in fact fairly independent as far as dogs go. They can be left alone for periods of time without developing anxiety like other dogs do.
When walking beagles, it is very important to make sure you keep a few steps ahead (visually) from the dog. Rosie would instantly sniff out other dog's poop, old burnt-out cigarettes, and even salt that had been sprinkled on the ground to combat early morning ice. This is especially important if you live in the city, where a dog that follows his or her nose is more likely to accidentally stick its face somewhere dangerous. It also means that carrying around high-reward treats will be the best trick up your sleeve: unless you have something that is a higher reward for your beagle, it will be nearly impossible to break their focus or attention on the item they so desperately want to sniff (or lick, or eat).