What are the most common mistakes to avoid when trying to gain muscle?

What are the best tips for gaining muscle mass? I've tried everything, from special diets to workout programs, but nothing seems to work. I'm even considering taking steroids, but I'm not sure if that's the right path to take. Can anyone offer advice on how to gain muscle mass effectively? I've been struggling with this issue since childhood, and it's affecting my confidence and self-esteem. Any suggestions would be greatly appreciated.