The Best Routine
A very frequent post on any exercise forum will look like this:
"What's the best routine for gaining (muscle mass/strength/size)?"
The parenthesis can be filled with other, similar items. "Bigger arms." "Bigger shoulders." What it comes down to is getting bigger and stronger.
Other posts will say "I'm just starting out, what should I do?" or something similar. Again, it's bigger and stronger.
I've answered my fair share of these. Here is the ready-made answer for cut-and-paste:
To gain (muscle mass/strength/size), you have to lift heavy weights, eat a caloric surplus, and rest. You need all three. Lifting heavy weights provides your body with a growth stimulus. The caloric surplus provides your body with fuel to react to that stimulus. And your body grows when you rest after training, not while you're training. So basically you lift heavy, eat well and often, and then sleep deeply and long.
Onto the specifics.
Lift heavy. You've got a lot of choices. You could make your own routine, or follow a published one. Or you could get a good strength coach with a track record of strong clients. The easiest path is to follow a published routine. Fortunately, there are some really good ones available free. In no particular order, here are some I've seen recommended over and over.
Workout Less & Achieve More by Mike Mahler. This one combines a few basic lifts with some fat-burning Tabata intervals.
Starting Strength, by Mark Rippetoe and Lon Kilgore. A famous routine with a long track record of success. It's based on three exercises a day, for heavy sets of 5 reps, done three times a week. You can read about it in its wiki, or just buy the book. You can read my review for more.
20 Rep Squats. An old routine, based on doing high-rep back squats with progressively heavier weight plus some extra exercises.
JV Askeem's Quality Series. A series of push/pull/squat routines. All very simple but excellent. No extraneous exercises, sets of 5 reps, and three days a week of lifting.
Stronglifts 5 x 5. This routine is based on squats, deadlifts, and presses. It's also available as a PDF and comes with its own diet suggestions. Also sets of 5 reps and three days a week of lifting.
Westside for Skinny Bastards 3. A template for athletes based on a famous powerlifting gym's workout principles. It mixes low-rep lifts for strength (sets of 3 to 5 reps) with medium reps (8-12 reps) and high reps (12-15 reps) for assistance exercises. It aims at building strength and size and strength-endurance all at once. The "washed-up meathead" template is especially good for non-athletes. If you simply must have curls in your workout, this is the one to do. Also available on PDF.
You can also buy a book with a routine - I'd recommend Nate Green's Built For Show, Eric Cressey's Maximum Strength, Lou Schuler and Alwyn Cosgrove's New Rules of Lifting, or John Berardi's Scrawny to Brawny, which also includes diet advice.
You'll notice all those routines have only a few exercises per day. That's a feature, not a bug. When in doubt, lift less rather than more. You don't need to pile on more and more exercises. If you squat heavy, deadlift heavy, do heavy chinups and bench presses...you'll grow. You don't need dozens of extra exercises...they'll just make you tired and add nothing to your growth.
You need to do these exercises correctly - regardless of what program you choose, find a good strength coach and learn the lifts. And buy Starting Strength and study its technique advice.
Now you could make your own routine, but if you really need to ask how to get bigger, you're admitting you don't know how. It's nothing to be embarrassed about. Just do a published routine written by someone who does know how, or find a strength coach. Not just a personal trainer at the local big-box chain gym, but a coach who has a track record of improving people's strength and fitness. It's better to look for a powerlifting gym, an athletic training center, or a private gym. Just call them and ask if they take non-athletes or non-competitive lifters; it doesn't hurt to ask and many of them are happy to take anyone who will work hard.
The only other critical factor is that you must log your workouts. Write it all down - what you lifted, how long you rested, how you felt. All of it. This isn't negotiable unless you don't really want to succeed.
Eat a caloric surplus. Again, you've got a lot of choices, but they all boil down to "eat a lot of food." You can't just eat anything, in any amount, whenever you want to. But you do need to eat. You need to take in lots of protein, at least 2g per kg of bodyweight, or more commonly 1g per pound of bodyweight. That's a very common recommendation...you'll see higher but not often see lower. You need a lot of quality protein to grow.
Do eat often - every 2-3 hours, have a meal with plenty of lean protein. After you workout, drink a protein shake.
Knowing what to eat is tough, and diet is always the hardest portion of training. Here are some places you can start:
Mark's Daily Apple's "Primal Eating Plan"
Dr. Berardi's The 7 Rules of Good Nutrition
Or check out this post
Maximum Strength and Stronglifts 5x5 come with specific eating advice. Starting Strength recommends GOMAD - A Gallon Of (Whole) Milk A Day, plus a full complement of 5-6 meals a day. So does the 20 Rep Squats program.
Stay away from any plans that call for steep caloric reduction and low-fat eating. You're trying to gain muscle and strength, not wither away! You'll need a big surplus on the days you train to encourage your body to grow.
Get your rest. You don't get bigger and stronger in the gym. You get weaker and tired in the gym, and you grow bigger and stronger while you sleep. Don't go lift extra weights on your days off, or run a few miles for bonus cardio. Get your sleep, at least 8 hours a night if at all possible. Take it easy on your days off. You grow when you rest, you recover when you rest. If you keep pushing hard between workouts, you'll slow down or stop your gains. You lift heavy enough to trigger an adaptation, eat enough to fuel the adaptation, and then when you sleep your body will make the most of those and supercompensate.
But what if I'm too big and want to get smaller?
If you're already big and want to lose weight, you can still follow the advice above - just ignore the "caloric surplus" and aim for a "caloric deficit." Read the same diet plans, just don't err on the side of too much food.
Really, that's it - lift heavy, eat a lot, and rest plenty. The specifics get tricky, but if you pick any of those workout plans and lift hard, and get your rest and eat your protein (or drink your milk, or both)...you'll have done all you really need to do to ensure growth. You don't need a lot of fancy supplements (aside from a good protein powder.) Save those for when simply eating and lifting won't do it.