Ignore 95 percent of the internet when it comes to training
Let me start off by saying that I think the internet is one of the most important inventions in human history, and it is a tremendous resource packed full of all the knowledge you could ever want about anything. The downside to this, of course, is that there is a metric ton of misinformation about everything.
When I first started lifting and training in general, all my knowledge came from the internet. I didn't have any experience. The one resource I did have—my elite level, retired, powerlifter uncle—kept telling me that I could do almost anything I wanted as long as I stayed to the core lifts and that I would get bigger and stronger. I thought to myself, "That must be impossible. Surely if I don't have that extra set of preacher curls my arms will never get bigger!" So I started googling the crap out of anything and everything. I became an armchair expert who saw circuit training as the 'end all be all' best way to do anything. Needless to say, I was sadly mistaken.
It's truly a blessing and curse to have the internet. On the one hand, you can get in contact with some of the top professionals in the field with the click of a button. On the other hand, you have people posing as experts, feeding poor advice to impressionable people who then feed that bad advice to others. You wind up with what you see in the majority of commercial gyms in America—a few people who clearly know what they're doing and the other 90 percent who think they do but in reality they're just squatting on stability balls like an idiot.
In summation, pick your sources wisely. Find out who are the top people in the field you want to excel in and listen to them. Just because someone you know is “strong” or has huge biceps doesn't mean they know how to train properly. Listen to the people who know what works because not only have they succeeded with it but others have as well.
Don't forget about flexibility
Flexibility is one of the most important aspects of being any sort of athlete. It ties in very closely with injury prevention, and many people (including myself) could have avoided some serious injuries had they given flexibility the attention it deserves. This means you need to make sure you have enough flexibility for whatever tasks you'll be performing as an athlete. As a powerlifter, my flexibility needs will most likely be different than that of a football or baseball player. Therefore, I should train accordingly. I have a friend who I train with every now and then. He's a big, strong guy with a good total, but he simply doesn't realize the warning signs of subpar flexibility. The kid can barely get down to the bar to deadlift. Even then, to do that he has so much lumbar flexion it's scary. Sadly, he's an injury waiting to happen.
There are guys who have shoulder/pec/bicep tendon issues from squatting because they lack flexibility. Just from our desk jobs and sedentary lifestyles, most of us have flexibility issues that are going to eventually bite us in the ass. Unless you take a head on approach to incorporating flexibility work into your training, you're going to regret it at some point down the road. This means performing a dynamic warm up along with stretches and foam rolling even when it hurts like crazy. Just like training for anything, when you put in the time now, you'll be successful down the road. Flexibility plays a major role in that.
Stop overanalyzing and lift heavy objects
Most of us have been there—trying to design the “perfect” training cycle or picking the perfect exercises, assistance work, and even band tension. But I have found myself trying to micromanage my training too much. The bottom line is if you want to get strong, make sure you're lifting heavy objects. Those objects can be barbells, stones, trees, kegs, cars, or whatever you want. Just make sure the basis of your program is lifting heavy. Speed work is great and a fantastic tool for lifting heavy items, but you also need to make sure you're lifting heavy objects.
I know the program in Muscle and Fitness says 3 X 15 curls and you can only use the 20-lb dumbbells without doing a power clean style curl, but try dropping the volume and lifting heavy objects. You won't be disappointed.
Don't stress out about eating clean when you're trying to get big and strong
I used to think that if I ate 1000 calories of pure chicken breast and salads while lifting I would not only get big and strong but all that size would be pure muscle. I mean c'mon—tons of lean protein! I'm gonna get huge. Turns out you have to eat more calories than you burn to gain weight (who knew?). Once I actually started eating things that had calories such as pizza and pretty much everything in sight, I actually managed to put on some serious size and strength.
The bottom line is if you want to get bigger and stronger no matter what, you're going to have to eat like a garbage disposal. If you're training your ass off four times a week, leaving the gym looking like you went for a swim, you're going to have to eat a lot. And eating chicken breast isn't going to have enough calories to get the job done. You need full fat mayonnaise, full fat chocolate milk, cheese on everything, bacon, more chocolate milk, and, without a doubt, more bacon. And if you're a hard gainer, double all that.
Too many people are so afraid of gaining a few pounds of body fat that they keep themselves from gaining serious pounds of muscle. Eat like a man. Chicks dig a barrel chest.
Hopefully, there's more to come as I try to remember all the stupid stuff I’ve done (there's a lot).
When in doubt, lift heavy objects until you can't anymore. Go home, rest, and eat. Then the next day, see if you can lift even heavier objects for more reps.