I want to have someone do a certain thing...what should the ad say?

Any advice about what ad to run, to have people apply to a webinar? Okay, so this question is, I'll rephrase it like this. I want to have someone do a certain thing. What should the ad say? Alright, that's really what the question is saying. In this case, Mark is saying, I want to have people go to a webinar, register for a webinar. What should the ad say? The question could be...