Stick to Basic Compound Movements
The core of your routine should be made up of exercises that involve the use of a large mass of muscle and the movement of several joints. Those exercises stimulate a lot of muscle and cause your body to release anabolic hormones. That means stuff like Squats, Deadlifts, Bent-Over Rows, Bench Presses, Overhead Presses, Dips, Stiff-Legged Deadlifts and Chin-Ups. These are the ones that will make you grow. If you go filling your routine with single joint exercises such as Lateral Raises and Triceps Kickbacks (because you want to "isolate" this muscle or that) you will only be wasting your valuable time. Put hard work into the compound exercises, on the other hand, and you will be rewarded with the fastest muscle growth possible. And it's not just my experience that proves this, but the experience of thousands of weight trainers throughout the years.
Eat More Good, Nutritious Foods And High-Quality Protein
Weight Trainers need more protein than the normal individual. Each weight training session causes your muscles to be broken down and rebuilt a little stronger than they were before. If you want to progress at the fastest possible rate then you'll need a healthy dose of daily dietary protein to fuel this process. 1 gram of protein per pound of bodyweight per day has been shown many times to be an optimum amount. Be sure you get that much, day in, day out.
How do you do that? Eat lots of stuff like eggs, milk, beef, tuna, chicken, cheese, liver, etc. Essentially, if it comes from an animal it's good. Get yourself one of those protein counter booklets at the bookstore or supermarket and pick out some high protein, animal-based foods. Then use these to meet your protein quota. It would also be a good idea for you to buy a protein powder. That's an okay 'supplement', but remember this: There's nothing that protein powder is going to do for you that a steak couldn't do (and probably do better). But the powder may allow you to mix up convenient shakes and it may turn out to be cheaper. Anything made from whey, milk and/or eggs will do fine.
You also need plenty of healthful fats, such as those found in fish and olive oil, to support and promote growth. You should eat plenty of carbs such as rice, vegetables and pasta, but avoid sugar and products laden with sugar. These 'good' carbs will give you energy to train and also provide your muscles with the energy they need to build yet more muscle.
Another thing, as soon as you get up eat a good breakfast. And that doesn't mean Pop-Tarts and Fruit Loops. Get some of the good carbs, proteins and fats that I spoke of above. After sleeping all night (and, therefore, not eating) your body needs nutrients to grow with. If you deny it that you will hamper your growth. Have some milk, eat some eggs, eat a steak if you want, but get some protein. Add a little oatmeal (it digests slowly and will hold you over until your next meal) and you have a good breakfast shaping up.
And eat some protein before you go to bed. Overnight your body will need protein, so give it some just before you go to sleep. It could be some meat, some cheese, a few hard-boiled eggs or something else solid. Solid proteins, generally, take longer to digest than liquids, giving a steady supply of amino acids to your body - so use them.
If you skimp on your nutrition you will cancel ALL of the growth that you stimulated in the gym. Yes, nutrition is THAT IMPORTANT.
Get A Good Amount of Sleep
Most beginner's don't realize this but let me assure you, sleep is just as important as training and nutrition when it comes to muscle growth. DON'T just skip over this rule and think it isn't that important. Critical repairs are made to the body and nervous system when you sleep. If you skimp on your sleep then you won't recover from your workouts properly and your nervous system won't fire your muscles optimally. Sleep deprivation results in reduced glucose sensitivity of the muscle cells and higher resting cortisol levels. There are reasons why training, nutrition and sleep are considered to be the 'big three' keys to weight training success. PLEASE, treat good, sound sleep as a full ingredient of your weight training program.
Limit Your Workouts To One hour
There are plenty of 'technical' reasons for that but this is not the place to get deeply into it. Let's just say that it's not necessary. Weight training is not an endurance event. If you want endurance go for a jog.
Don't Train More Often Than Three Days Per Week
"But Ronnie Coleman trains 6 times", I can hear you saying. Unless you are very genetically gifted, you do not have the hormone levels to train that often and progress maximally. It's true that some advanced drug-free athletes can train 5-6 times per week but those routines are NOT appropriate for you at this stage. Generally, drug-free strength athletes make their best gains when they spend more days out of the gym than in. Don't believe me? Hey, it's your life, do what you want - but if you don't listen to this you'll regret it. I've been there.
There's no need to train more than 3 days per week at first. Genetically gifted people will just progress faster on that 3-day program. So, if you are genetically gifted, a 3 day per week training program won't hold you back. But if you are not it might make the difference between some gains and no gains.
When you get more advanced you might end up adopting longer routines (though not necessarily), but, for now, anything over an hour means you're loafing around too much or you're doing more work than a beginner's body is likely able to tolerate.
Strive For Perfect Exercise Form
Cheating your reps builds nothing but ego - not muscle. If you have to cheat that means the weight's too heavy for you to lift properly. Cheating does not make a muscle contract harder because you can use heavier weights. A muscle can contract only so hard and that's that. All cheating does is bring other muscles into the movement so that you can use more weight - that's not how to effectively train a muscle. Besides, cheating can be DANGEROUS. Proper form is safe. When you start deviating from proper form you open the door for a potentially serious injury. Even minor injuries can cause you to miss workouts - and that's certainly not an effective way to gain muscle.
Ignore The Guy Next To You
This rule ties in closely with the rule before this but isn't quite the same. Here it is: Don't be insecure. If you're lifting this puny little weight and he's lifting 5 times that amount (or even 100 times) WHO CARES! He's not you, you're not him. Don't start cheating so you can use more weight. If he's using bad form and cheating a lot then that's his mistake. Remember the tortoise and the hare. If you work hard enough, long enough, and never, never, ever quit, you'll get there too - and with proper form.
You have to swallow your ego. I had been training for almost 15 years when I decided to learn the Olympic-style Lifts (the Snatch and Clean and Jerk). I had to go from Squatting 445 pounds to Snatching 65. Do you know how foolish that made me feel (and look). Remember, "A journey of a thousand miles begins with a single step." Do what's right for your body, not your ego. HAVE PATIENCE!
Genetics Do Make A Difference - But WHO CARES!
Some people will progress much faster than others. Some people will grow into solid chunks of muscle within a few months, while others will have to work for years to get half the gains. I've seen it a thousand times. And it's not just training routine design, effort, desire or diet. If these things were all equal it would still happen. But there's nothing you can do about it - so GET OVER IT. You can only work with what you've got, so do that. I've seen some very genetically gifted people come into the gym and pass my strength and muscle level within 6 months of steady training - and I've been doing this for over 12 years - but I lived. And I'll be in the gym again tomorrow.
Avoid Those Exercise Machines
That means no Shoulder Press machines, Cable Curls, Pec Decks, Biceps machines, etc. If you want to build the most muscle possible, as fast as possible then you will have to lift free weights. Oh sure, there are all kinds of so-called 'scientific' arguments why the machines are better, but, believe me, there are also a lot more sound scientific reasons why free weights are. And I have one reason for you right now: If you spend your time on those machines you will SEVERLY limit your progress. Reason enough for you? I spent YEARS wasting my time - and so have countless others. Don't become one of those people who hits yourself in the head a little (or long) ways down the road and says, "Why didn't I do the free weights in the first place? Look at the time I've wasted!"
What makes the machines so appealing is that they are easy to learn to use, and comfortable when you do use them. But comfort is NOT what builds muscle. And what good is something being easy to learn if it's not worth learning in the first place? The free weight movements will take longer for you to learn but you will be more than rewarded when you do. If you don't believe me then feel free to waste your time.