I recently completed a direct mail piece in which I ran into something that I run into frequently -- the overwhelming desire of a business owner to tell absolutely everything about their business in a marketing piece. And their absolute refusal to edit the copy.
An ad in any form, be it print, direct mail, TV, web banner, whatever, is meant to be a teaser. Something that will entice a customer to visit your place of business or your website. Really all you need to tell them is who you are, what you do and what makes you different from/better than the others. If that appeal is well done, the customers you want will respond.
Your website, your office or store, and YOU on the phone or in person is the best place for people to find out more about you. A marketing piece will never sell you as completely as you do yourself.
This is all beside the plain fact that there's not a lot of room to work with in an ad or even a brochure (or a radio or TV spot, for that matter). This direct mail postcard ended up with four paragraphs of eight point type on the back, plus a coupon. There is no way I'm going to wade through all that when I get it in the mail. The coupon will catch my eye, but the rest is yadda, yadda, yadda.
Oh, yeah -- I forgot to mention that included on the coupon is a QR code that links you directly to the website, and the website URL. Where the owner says all that stuff again. If I take the time to go to your site, the least you can offer is some new information.
The upshot here is listen to your designer or marketing person when they tell you to think in bullets and headlines. The rule of thumb is that people look at something for no more than three seconds before they decide to stay or move on. Give your audience just a taste of who you are. You have other outlets that they can go to for more information -- the best one being you. That's why we make the phone number so big, eh? 
