Hiking is one of the best things you can do to get your heart pumping and your muscles working. You don't have to hike a mountain in order to call it a "hike." If bad knees are your problem, stick to level ground. Going downhill really does a number on your joints.
Tips for a smooth hike...
Hike with a Friend - Never hike alone. There's safety in numbers. Speaking of numbers, it's a great idea to carry cell phones in case someone gets separated or hurt.
Plan Ahead - Know the terrain. Get a copy of the trail map so you know what to expect. A Hand-held GPS isn't a bad idea either.
Dress accordingly - Wear waterproof hiking boots that are high enough to protect your ankle. If it's cold out, wear lots of layers. Once you get moving, you'll quickly want to shed the warm stuff so you don't overheat.
Fit's Tips: Don't forget to bring a lightweight camera to save all your memories.