Alright, to start off, this article won't be about "miracle" solutions that will help you get into shape in three easy steps. We're not gods, we're mortals. Therefore, if we want something bad enough, we have to actually put effort into it.
In this case, we're talking about gaining/losing weight in a healthy fashion, and not simply getting more muscle mass for the purpose of looking good. Yes, looking good is there in the equation, but the appearance should be a byproduct, not the end goal.
After all, if you get a Mr Universe body via steroids and other similar synthetic muscle boosters, but wind up dying as a result, all you'll be in the end is a good-looking corpse. Not a good idea, if you ask me...
So aim for health first, functionality second, and appearance last. That's my advice to those who want to build muscle mass and/or burn off fat.
Moving forward, let's talk about health first - before engaging in any strenuous physical activity (and you'll need to if you're serious about getting into shape), meet up with your doctor for a quick checkup to make sure you can actually do so without risk.
Also, check your personal eating habits and any detrimental vices you may indulge in. Eating a balanced diet with carbohydrates (rice, corn, or bread), protein (meat), and of course, vegetables, is a good foundation for health. Low-fat milk adds needed calcium which helps strengthen your teeth and bones.
Once you've taken your food consumption into consideration, think about any vices you may indulge in. Smoking and alchohol top the list of common vices that have adverse effects on health and, consequently, your physique. If you smoke or drink (or both) and can't kick the habit, then at the very least minimize.
The next thing to consider is that wonderful little word that usually separates the people who dream about being in shape and those that actually get into shape... Yes, i'm talking about exercise.
For starters, before considering weight training for building muscle mass, I would recommend getting your cardiovascular system into shape. Improving your heart and lung capacity in this fashion extends your overall endurance not just for weights, but for any and all physical activity you engage in.
One tip: Breathing is the key. Singers are trained in this, as are martial artists and swimmers. Breath from the diaphragm, meaning when you inhale, your abdomen should expand, not your chest. This increases the circulation of oxygen in your system. Once this manner of breathing becomes instinct, then you can start on running for cardio training.
Some people advocate power-walking or jogging, but a long, loping run that utilizes ground-eating strides is actually healthier. Various studies have shown that power-walking and jogging actually place undue stress from impact shock on a person's ankles and heels.
Go instead for an easy run. Don't try to go fast on this, the key to running is to maintain a constant pace. Strive for consistency, not speed. Start off with half an hour of running a day and gradually increase your time spent.
After a month of running, you should be ready for the next step in building muscle up; weight training. Head off to your local gym; getting a home weights set may sound good, but in reality if you're serious about it, you need guidance from someone who's been in it longer.
There are 2 ways to go about weight training depending on what kind of physique you want to get: for those who are after muscle density, in other words the "lean and mean" look, use lighter weights with higher numbers of repetitions per set.
For those who are after sheer bulk and muscle mass, the "bigger and badder" look, use fewer repetitions in lifting but with heavier weights. These two systems actually dictate the shape of your muscles; the first approach makes your muscle fibers longer, thinner, and denser, while the second approach makes the muscles shorter but thicker.
Whichever approach you choose, the important thing in gaining/losing weight and getting in shape is to have the self-discipline to make proper diet and exercise a part of your daily routine.