Design is about realizing an intention, including things that accomplish your goal, and eliminating things that interfere with it, or just take up space. Here's a basic recipe for making it work, whether it's a flyer for an event, an ad on television, a billboard, whichever. Address these issues in order, no skipping ahead. Consider especially that the recipient/viewer is easily bored/distracted and really couldn't care less, and bring it all to them: what are they looking for, what do they want? You may be very excited about what you are offering, but they are the ones deciding whether or not to participate. Continually re-evaluate your decisions from this point of view.
market/context: who are you trying to reach, and what is the medium, and context? for example, a flyer for college students on a table in a bookstore requires a very different form than a magazine ad for woodworkers.
intention/mission/message: what are you trying to impart/accomplish? the more you can articulate this, and simplify it, the better your chances of a successful contact.
within the event/designed experience, these are the four steps:
attract attention: if they don't pick up the flyer, or if they leave the room or look away when your ad comes on, you lose.
sustain/shape attention: if you attract/create attention, three seconds later you have to do it again, and after the second time, you have to do it a different way. create a hunger then answer it, and lead them to the realizations of your choosing.
call to action: what do you want them to do? go to a website? crave your product? feel strongly about an issue and act? you've created the desire, now specify the way to fulfill it.
takeaway: what is the feeling they leave with? excited? creeped out? There was a Taco Bell ad where some guy is sorting baseball cards and some other guy puts down a bag of food, and they say oh no, etc. The takeaway from this, no matter what the talk about new items/prices, whatever, is that the bottom of the bag is greasy, period.
see also Feng Shui and How to Solve Problems