concentrate on form! try not to just muscle your way up the wall - use good footwork, proper body positioning, etc etc. strength and muscle is certainly important, but you can accomplish a lot just by using good technique.
listen to your body! know when to take rest days and when to push harder. if you feel something tweak in your fingers or elbows especially, be cautious - those could lead to serious and long-term injuries.
don’t worry about the grade! this is one I’m still learning. I think this applies especially to stuff that you deem “too hard” for you. if there are cool moves on a V8 that you think you want to work, then work it. forget the fact that it’s a V8. working those moves will make you stronger. same thing goes for routes.
climb with people who climb harder than you! it may be intimidating, it may be embarrassing at first, but this is one of the best things you can do. make friends with stronger people, with people with better form. just by watching them climb or having them give you advice/beta will help you a lot.
don’t forget to breathe! I know this might sound a little stupid, but it’s true. make sure you’re breathing while you climb. it helps you stay relaxed, focused, and on the wall. holding your breath does you no favors.
stay relaxed! physically and mentally. don’t overthink, don’t overgrip. try to stay as loose as you can, focus on each move, not what’s coming 15 moves ahead of you. rest when you can, shake out, chalk up, do what you need to do to maintain a fluid, efficient climb.
have fun! climbing is supposed to be FUN! whether you’re projecting the climb of your life, competing at the world cup, or just warming up, you should be enjoying yourself. don’t compare yourself to others, and don’t let other people around you affect your self-esteem. you climb because you like it, right? that’s all that matters at the end of the day.