Check out this web site ExRx (Exercise Prescription) on the Internet. It is nothing fancy, but is loaded with good solid information on nutrition, technique and programs. A push, pull, leg program is a good place to start. Changing things up every six weeks is a good thing. Identify your body type, set your goal(s), educate yourself, and eat according to your goal. Do not worry about getting big, it is extremely difficult unless you are eating huge amounts of food and getting extra "Help"

I was doing the "burnout method" when I stopped. Basically, to warm up I'd hit the machines and start with around 15 pounds ten reps, 20 pounds ten reps, 25 pounds ten reps, then all the way down doing 5 reps until I stacked the whole machine. I'd do that for the bench press, military press, pec deck, quads, hams, calves, and bicep curls I'd work up to around 140 or so. Then I went to free weights and did the same with dumbbells. It was a crazy insane workout, but it took me probably 4 years or so to get into that kind of condition.

My point that I want to make is that everyone works at their own pace. The absolute worst thing you can do is to injure yourself, by working too fast and being impatient, using bad technique, or not warming up, or not eating and resting right.

Take your time and learn first, then you can go full agro after you're in top shape.

Somehow I'm 50 years old and along the way I've learned that whenever I have a training-related setback it's always the connective tissue, ligaments or tendons. I cannot recall a muscle itself getting hurt, but I've lost plenty of workouts over the years due to bicep/elbow tendonitis, shoulder impingements, and spinal nerve radiculopathy. All of them are exacerbated by heavier weights at lower reps. It can be very hard not to load up the bar when you're banging away, droppin' plates, feeling good and the weight feels light. Must resist...

Good advice from Oracle above ^^.
What I put into the mix now that I'm old - Cut way back on the free weights, use weight machines in the slow/negative method. Use TRX straps system for core and stabilizing muscles.
Doing this seems to save me from reaggravating old injuries. And causing new ones.
It probably won't help you bulk up after a lot of free weight work, but it will break the routine, maintain the muscle mass that yo already have, be a little easier on the joints, get you feeling good and mobile, and have a very low chance of an injury while working out.
Good luck!!

I agree and thank you for mentioning deadlifts.

If you have never done them before, they are a game changer. Just do not start out with too much weight, if your lower back aches give it a break (a week's rest) and do lower back and back exercises to catch up.

Excellent advice.

When I hurt myself (tendon in arm near elbow) it set me back some, but I found swimming was no problem, did that exclusively for months. My lats are probably the strongest part of my torso as a result, not bad, not good, just the way it worked out. If you want a "V-Shape" hit the pool.

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One person I talked to with an impressive build told me there are only three exercises you need.

1. Deadlifts

2. Squats

3. Pull-ups / Chin-ups

You cannot go wrong with these as a base point, but to catch up after years of being dormant you are better off keeping your body guessing about what you are going to throw at it next.

Think about the hardest grade school teacher you had, chances are they kept you guessing and threw pop quizzes at you constantly. Same thing applies to your body as does your mind.

Challenge, challenge challenge, and don't get complacent.

Oh. and go at your own pace like others said. This is one reason many of those Youtube videos are dangerous, they push you too much.

Same here.

I think there is a far less chance of stressing your joints and tearing tendons if just using your own body weight verses using heavy weights.

Important not to ignore the warning signs and to continue to do something which results in repeated irritation. I retired my bench press for that very reason (rotor cuff discomfort), using dumbbells from the floor now - much better.

The rest periods are just as important as the workouts.