The most common mistakes beginners make in the gym
I've been training for 3 years without a coach, and every mistake on this list comes either from my own experience or from watching other people.
Thinking you need to lift heavy to build muscle.
Looking for the "perfect" workout program.
Expecting fast results.
Setting unrealistic expectations.
Not paying enough attention to your nutrition.
Comparing yourself to Instagram fitness models.
Avoiding the big compound lifts (squat, bench press, and deadlift).
One more thing: don't waste your time looking for 100 different exercises for the same muscle group.
Master the basics with one or two exercises first. Learn proper technique, understand how the movement works, and only then move on to something new.
Every exercise has its own technique, and if you're a beginner, chances are you won't perform it correctly right away. If you keep jumping from one exercise to another, your progress will be much slower.
Bonus:
If you're a natural lifter, chances are you won't look like the top fitness influencers on Instagram. And that's okay. Don't get too upset about it... or just join the dark side. :)
And remember: nutrition is responsible for a huge part of your results.