First, the ground rules: I am assuming that you are an adult who wants to change another adult’s behavior. Parenting is another issue, thought I think some of the ideas are applicable. Second, I assume that it is REALLY REALLY important to you that this person change their behavior, the person is an important part of your life and their being late all the time, or whatever it is, is really driving you nuts.
Step 1. Let go of the idea that you are going to be able to change the other person’s behavior. Sit and contemplate that for a while. Get comfortable with the possibility that the person will never, ever change, because in all likelihood, they will not. How would it feel to simply live with the behavior? Is it possible you could change your own behavior and attitude to accommodate them? Desperately nagging someone to change is the quickest and surest way to completely sabotage your efforts. Once you truly accept that they may never change, you can use this strategy without grasping and desperation. If you cannot accept the behavior, then prepare yourself emotionally to abandon the relationship.
Step 2: Make your feelings about the behavior very clear to the person. “When you are late, I feel like I am not a priority to you, and that hurts my feelings.” Give specific examples. “When you were late meeting me last week, you made us both late to the Bon Jovi concert and we missed the first song. I was really mad about that because I love Bon Jovi and those tickets were expensive.” Once you are sure the person has heard you, back off and do not go over this again. If you have already been complaining to the person about how their behavior makes you feel, then skip this step.
Step 3: Ask for what you want. “I want you to arrange your schedule so that you are sure to be on time to meet me.” “If you are unavoidably delayed, I want you to call me and let me know what’s going on, so I can decide whether to go without you.” The back off and do not go belabor this. If you have already been telling the person, calmly and clearly, what you want, then skip this step. They already know.
If you have been suffering in silence, or trying to drop subtle hints, then steps 1,2 and 3 may solve the problem entirely. Alternately, look for a way to work around the behavior. Would it work to simply tell the person a time to meet you that is a half-hour earlier than necessary? Is there something that could be purchased that would solve the problem, for example, if your complaint is that the person will not clean the litter box life they promised, can you buy a self-cleaning one? If they won’t dust, can you afford maid service? If steps 1,2 and 3 havent’ solved the problem, and there’s no work-around, then proceed thusly. This is where it gets tough, and takes time:
Step 4: Praise good behavior. I recommend lavish, enthusiastic praise in whatever form the person understands best. Physical affection if appropriate, kind words, gifts, doing things for the person, etc. Connect the good behavior to you being thrilled with them and their life being better as a result.
Step 5: Ignore bad behavior. That’s right, I said ignore it. You have already been very clear about how the behavior makes you feel, and what you want the person to do. You have accepted that they will not change, right? Right? So it’s really no skin off your nose. Do not punish, simply withhold the praise and appreciation and go on with your life. Decide how you will react to the behavior in a way that keeps you from being irritated. For example, if you make a date to meet this person at 2:00, know ahead of time that they are going to be late (you will be pleasantly surprised if they aren’t), and decide for yourself how long you are comfortable waiting before you leave without them. Then do it.