It's relatively easy to spot shiny metal brake lines, so follow those to the less obvious hoses, which are tucked out of the way behind the wheels, attached to each set of brakes. You'll probably have an easier time finding the brake hoses if you jack up the car enough to remove each wheel in turn, and if you really have trouble spotting them, you can always check your car's service manual.
Once you've found the hoses, a good visual inspection will help you familiarize yourself. Any of the following indicates wear: chafing or cracking, drips or wet stains, bubbles, blisters, and bulges. Make sure the hoses are mounted properly and securely. Look for and follow two lines printed along each hose. Wavy lines indicate the hose has twisted -- it either has too much slack or its mounts and fasteners might be failing.
Next, feel the hose. (Make sure the car hasn't been running recently, so you're not grabbing hot parts.) A good hose is strong but not stiff, firm but not brittle. Very soft hoses are too weak to work well and probably decaying; hoses that are too hard can't cope with a car's normal operations for long, and they're likely to crack or burst under stress.
Even if everything looks good so far, you're not done yet. Grab a friend for the next part of the brake hose test.