Just some very basic suggestions that I've found where absolutely the most helpful since I started seriously working out.
I've been working out for almost 4 years, and honestly I have grown 25 pounds of mostly muscle in the last 2 months, because.....
-Get a trainer who is much bigger than you, and trains several other people. My trainer trains fitness comp women, teenage girls, pro competition bodybuilders, bouncers, basically anyone interested in msulce fitness, and he knows tons. Even if its just to have him/her write you a diet/workout plan and monitor your progress every now and then, its worth it. Knowledge is power (and size)
-Be prepared to eat. Bodybuilding is done at the dinner table as much as in the gym, you don't diet, you aint gonna grow (I'm 6'4 and have a fast metabolism, I need to eat like a freaking horse just to see the slightest gain like 5000+ calories a day every day, and I'm only 251lbs).
-Try to eat clean (skim milk, chicken/turkey breast, rolled oats/oatmeal, potatoes, whole wheat pasta, rice, peanut butter, tuna, veggies, water, etc) but let yourself cheat from time to time. You see some pizza you want? Grab it, this kinda depends on your metabolism also(my body does'nt like to put on fat so I got more room than some guys do, who just look at fat and it goes to there abs). Just make sure you eat ALL you diet food before you ever eat anything else. You absolutely MUST get more calories than you body needs to gain serious size. You can lose fat later.
-Make sure you focus on your real food before supplements, you need to have actual solid food constantly in your system to grow, I have 3 whole food meals, and 2 supplement shake meals per day (5 meals total spread out every 3-4 hours if I can) I would say thats minimum, some guys eat 6. If your trying to get super lean you probably will eat more meals than that, just with less but cleaner food.
-Work out hard no more than 5 on 2 off, or 2 on 1 off. You need to rest.
-Make sure if your going all natural to stick to a lot of basic heavy excersizes, like squats, leg press, bench press, shoulder press, bumbell flies, curls, etc. Don't try any crazy 21's or lunge squats or anything weird and complex until you have done huge amounts of the basics.
(this is just my personal way of working out, others do it differently and still get results....)
-If you go in most gyms your gonna see some guys (usually the sorta big to very big sized ones) pounding out reps will massive weight with a buddy behind them spotting them while viens pop out of there head and they moan in pain. Thats because the only way to grow is to constantly shock you body. You lift 20 pounds all the time, you gonna look like 20 pounds. Increase your weight each set and make sure you last set goes either to failure or to the point where you muscles get shaky and weak feeling, finish out that set and thats it for that excersize. Pretty soon you'll be lifting huge, you'll be strong and big, and you'll know it, and other guys will know it. Also every 4-6 weeks your gonna have to change your entire excersize program, you body will adapt to the excersizes your doing and you gonna need to use different ones. As an all natural bodybuilder you going to feel almost like your starting powerlifting, you need to lift heavy to get results.
-Remember, if your all natural your gonna have fat, even pro bodybuilders with steroid use get some fat when they bulk up, so much more for all natural(unless you got awesome genetics), but you won't have a classic gross fat look, you will be big and bulky with a bit of a gut maybe(depending on how clean you've eaten and metabolism), nothing to worry about at all, and when you decide to cut up your gonna be so much bigger than those "stay lean and gain slowly" guys it won't even be funny. If you eat ultra clean, chances are your still gonna gain some fat, extra calories always means some fat gain regardless where you get it from, its just calories from fat store more than calories from excess carbs/protien. Your either anabolic (creating more complex structures like fat and muscle) or catabolic (breaking down those same structures) without roids your not gonna have both.
Thats just my two cents. Honestly the most important thing I would say is get a trainer, you body type is going to be different than mine, so some of my info or other peoples info might not apply to you, you need someone you can sit down with and talk about working out, and ask questions. The more question you ask, the faster your gonna get big or lean or whatever you training for.