>>15976711. Buy shoes that are tight, but not so tight that you can't stay in them for an hour. If you have to take off your shoes all the time then you waste time on the wall.
2. Don't do full crimp. Do open hand crimp or half crimp. (in pic do A or B, but not C). You will just get injured for no good reason. If you can't hold something without full crimp yet, then just do something else instead.
3. Don't always jump down from full height, your back and knees will thank you.
4. Stretch and warm up before climbing
5. Stay close to the wall
6. Don't overgrip holds, just use as much strength as necessary
7. In overhangs try and keep your upper body parallel to the wall, don't let your ass hang out.
8. The fastest way to improve is to spend more time on the wall. Sometimes it's better to do many comfortable boulders than struggle with one harder one for an hour.