We have a four year old female beagle, whom we got when she was about five months old.
They are very hard work! I second everything pingu says.
They are strong willed and stubborn.
There is a saying "If you see someone walking with a lead but no dog, they are a beagle owner".
They are obsessively greedy and food-orientated. Once dressed, they put on weight easily. ours is on a constant diet.
We took ours to dog training, and whilst I am glad we did, it was the most humiliating and stressful experience!
Ours has been well trained but her recall is still shit. We are lucky in that we can let her walk and run off the lead, but only in places we know, or secure areas. They are well known for running off. If they pick up a scent of something they go mental and are off. We lost ours a few times when she was younger but luckily she is a bit better now.
They will chew anything in sight. I have lost count of the number of chewed shoes - it is not something that they necessarily grow out of like a lot of puppies do. I have lost two pairs of glasses which she has chewed to pieces. It has more been a case of retraining ourselves, rather than training the dog - all shoes in hall cupboard, bedroom doors shut, try and keep food out of her reach (impossible, she will leap on tables if there is food there and will also steal food from out of your hand, and your mouth if she can!)
She is really friendly and great with other dogs and people, really snuggly and we just love her to bits.
However, I would not recommend that anyone gets a beagle if they don't at least have experience with dogs. Quite a lot of people come up to me and say they would love a beagle because they look so adorable. DON'T BE FOOLED!