Size
First, there is little difference between the two Beagle varieties (13" and 15"), which are born into the same litters.  Depending on genetics, some grow to 13" and others to 15" measured at the shoulder. The 13" variety usually has less bone mass, but in both varieties the preferred dog is one with sturdy bone structure. This translates to a dog who should weigh between 20 and 30lbs depending on bone and muscle mass... and diet.

Weight-watching is important, because a beagle is ALWAYS hungry. Their table manners are those of the typical hound: if they can devise a way to get it, it's theirs by right- all part of the game. They won't have a clue why this should upset you, and although they may be very unhappy the "lead dog" (that's you) is unhappy, they're simply not going to believe it's because you'd begrudge them a Christmas turkey! They strongly consider the last person to feed them, their best friend. 

Appearance
The most common color combination is called tri-color. It means a black saddle, white legs, chest, and belly, with a tan head, and tan around the edges of the saddle. Many dogs have a white blaze on their face, but a solid tan face is common too. Tri-color puppies are born black and white - tan develops as the puppy gets older.

Red and White: There is no black at all, and the red can range from a light tan to a darker red. These puppies are born as red and whites, or sometimes even a solid white, with the color developing later.

Lemon and White: The lemon varies from an off-white, to a dark lemon. These puppies are often born completely white, with the color developing later.

Black and White: Very rare.

With all of these colors, you can have freckling, mottling, ticking, and grizzling. Occasionally, an all-white hound appears, but this is very rare. These are not albinos, simply white dogs.

Temperament
Beagles are scent hounds, bred to track prey over the countryside and then to flush it for hunters. This requires energetic, independent, creative, outgoing, and sometimes stubborn dogs who devise, execute, and follow a plan to it's conclusion. A lone Beagle requires substantial playtime and attention. Without stimulation from their 'pack', beagles will amuse themselves - and this can mean trouble. Beagles can do astonishing damage!

Beagles have loads of energy and are well-suited to those accustomed to regular exercise. Bred to run cross-country in pursuit of rabbits and foxes, they enjoy long runs and demand regular exercise. In rare cases, Beagles can be kept in apartments, however, you must be extremely dedicated to taking regular walks, and it is not advised. On the other end of the spectrum, keep in mind that you should wait until the dog is at least a year old before (slowly) starting a prolonged running program of more than a mile per day. Talk to your vet for more information on running with your dog.

Although they love the outdoors, Beagles do not make good 'outside' dogs. They need to be kept occupied and if regularly left in a backyard, will usually dig, bark, explore, experiment, and contemplate escape. If you are dedicated to walking in the morning before work and spending lots of time with them when you get home, your beagle should be able to spend an hour in a securely fenced yard.  "Invisible" electronic fences will NOT work- Beagles are far too curious and too devoted to "the hunt" to pay attention to (what they consider) minor corrections.

Most owners keep their dogs inside when they're unsupervised for long periods.  Crate training is the most suitable arrangement unless a sturdy, indoor/outdoor run can be arranged. In most cases, and for reasons including risk of theft, escape, or torment by neighborhood children and dogs, having a secure indoor place for your Beagle is the best arrangement.

Personality
Beagles were kept in packs, resulting in a strong need for companionship from another dog or from you. They consider everyone a friend. Happiest in a group, beagles love to party and won't be unsettled by new visitors, friends, and family. They'll be delighted to meet every friend and relative you and your family bring or meet on the walking path, and are an excellent member of today's busy families- so long as everyone understands that the dog NEVER leaves the door to an unfenced yard without a leash.

Beagles generally get along well with other dogs and cats and adore children, especially if they are socialized properly with them (test the waters carefully- a small cat looks a LOT like a bunny the beagle was bred to hunt!)  Beagles should not be aggressive towards other dogs, however, they will protect their seniority by growling and other posturing. Beagles should *never ever* be aggressive towards humans. That said, small children and dogs should never be left unsupervised. 

Beagles are not very territorial, so they rarely bark except when bored or to announce visitors. (ed. note: You'll find show-bred beagles quieter than "field beagles"- some puppy owners have never heard their dog bark!) 

Their intelligence and independence will lead them to try to dominate the family, setting their own rules for "on limits" and "off limits" areas, behaviors, and activities. You should not allow this and if you have problems, see a good dog trainer to learn how to correct them. 

Training & education
As stated in the frequently asked questions section, the Beagle's independent and stubborn nature makes obedience training a necessity. Be sure to get into some kind of training routine early in your Beagle's life. If you attend obedience classes, make sure your instructor understands the hound personality. Beagles require a firm trainer, but not a physical one. Beagles neither respect nor acknowledge physical force.

Health Issues
Beagles, like all breeds, should be bred carefully and by knowledgeable people to help minimize hereditary disorders. Some disorders that are found in Beagles are:

Eye Disorders
Cherry Eye -- Very Common swelling of the gland of the third eyelid Glaucoma increase in fluid pressure inside the eye Cataracts -- clouding of the eye lens
Retinal Dysplasia -- folding or displacement of the retina, may lead to blindness
Progressive Retinal Atrophy -- cells of the retina deteriorate over time causing blindness

Other Disorders
Epilepsy -- Very Common brain dysfunction resulting in seizures Elongated Soft Palate soft palate at the back of the throat is elongated and interferes with the larynx
Hypothyroidism -- Very Common Dysfunction of the thyroid gland, causing numerous clinical signs including weight gain poor hair coat, reproductive problems and more. Cleft Lip and Palate opening between oral and nasal cavities, can impede pup from nursing
Monorchidism one testicle does not descend
Cryptorchidism both testicles do not descend
Intervertebral Disc Disease degeneration of the intervertebral discs, causing severe neck and back pain
Pulmonic Stenosis heart defect, may cause heart failure
Kidney Failure
Bladder Cancer