Provide evaluations for whatever class, process, or experience you have been teaching, or in which you are interested in knowing the results. The evaluations should go to the participants, or, in a classroom setting, should be given to the students so that they can grade you.
Conduct the evaluation with the intention of learning how you can improve. If you are giving a survey to members of a training course to ask them their opinion about the course, give them the survey and read the results. If you are giving your first graders a test to evaluate how well they've learned the unit on addition, give them the test and then grade it to figure out how well they've learned.
Gather the results of the evaluation, whatever form you have used. Then analyze them in order to learn from the evaluations. Learning from an evaluation is straightforward. If you gave out a questionnaire to evaluate your performance in a play, simply read what the evaluators had to say. If you gave out a test to evaluate your students' performance, grade the test to see how well they did. The information you get from gathering the results of the evaluation will allow you to learn much of what you need to know about whatever you were evaluating.