In addition to the advice one usually gets (get a checkup before diving into a weight-loss program, be careful with diet pills, don't starve yourself), I'd like to stress the importance of exercise. A lot of people have put on weight because they sit in front of a computer all day and city planners have deemed it important that people be forced to drive to their workplace rather than being able to safely walk or bicycle there.

One exercise, in particular, is extremely beneficial for people who are out of shape or have joint problems to the extent that vigorous sports or aerobics classes are a bad idea: walking.

If you've been sedentary, I guarantee that you'll lose weight if you start walking at least 45 minutes a day (provided you don't start consuming more calories, of course). You won't drop a lot all at once; this is a gradual, steady kind of weight loss. Regularly walking at a brisk pace (2.6-3.2 miles per hour) will also get your body in shape for more vigorous activities. And you'll get a bit of sun and fresh air.

Don't let bad weather or allergies stop you; most indoor gyms have walking/jogging tracks and/or treadmills. Treadmills, of course, can be deadly dull; try reading or watching TV. If you have the funds, you might consider purchasing a treadmill for home use (try looking for a used one first). A much cheaper alternative is a jogging trampoline: you can get one for about $20US at Wal-Mart, and they take up much less space than a treadmill. Challenge yourself to not watch TV unless you're also walking or jogging.

Swimming is another excellent exercise; it's easy on your joints, tones your muscles and improves your cardiovascular system. However, some people find that swimming in cold water makes them very hungry afterward, and the urge to hit the snack machine may undermine your efforts to lose weight.

The key to losing weight is to try to keep active and raise your metabolism while you reduce your calorie intake. You'll also lose more weight if you spread your calories out over 5 or 6 small meals during the day than if you skip breakfast and gorge on a big dinner. Continually "grazing" throughout the day helps keep your insulin levels steady.

A simple thing a lot of people can do to reduce calorie intake is to quit drinking Coke and other sugary sodas. If you drink soda all day, you could be consuming hundreds of empty calories as well as possibly putting yourself at a greater risk of developing diabetes later on. Switching to diet sodas works for some, but artificial sweeteners taste bad to some people and may be unhealthy in the long term. Try switching to teas and juices (the 100% juices -- fruit juice cocktails are loaded with extra sugar). Green tea, in particular, has been found in lab studies to promote weight loss by raising your metabolism slightly (this effect was independent of its caffeine content).

Anyone trying to lose weight should drink lots and lots of water. Some people feel hungry when they actually need water. Water helps fill you up and flushes out toxins. It also greases the biochemical wheels that help your body's metabolism work to its fullest.

A lot of us are either too busy or too unmotivated to cook. A lot of us eat out of snack machines. If you can't quickly change where you eat, try changing what you eat. Choose fresh fruit or yogurt or pretzels over potato chips. Nuts like peanuts and almonds are good because they contain fiber, protein and minerals -- they are high in calories, yes, but studies have found they are overall less fattening than sweets with equal calories. Also, try consuming more salads and non-cream-based soups. If you have a place at work or school where you can store your own snacks, bring in instant vegetable soup cups (look for types with higher fiber and lower sodium). These will fill you up more and feel more satisfying than many other kinds of snack foods.