The best way to do that is by practicing – climb, climb, and climb. Start, of course, with easy routes. You are not in a controlled environment anymore. You have many factors playing a part – falling rocks, weather, sun exposure, not knowing where the holds are.
To help you figure out what climb you should try to conquer, use the rating system. The ratings range from 5.0 (extremely easy) to 5.14e (hardest). Since this is probably not the first time you’re rock climbing, most of the routes on this list range between 5.3 and 5.8. They are still described as “easy” and “fun” by climbers.