=> USE A LARGE FONT. It makes more impact and is easier to read. It also makes your handout larger which makes it appear more substantial.
=> LEAVE LOTS OF WHITE SPACE. I had a complaint recently that said there was not enough space to write notes. I usually deliver very high content so this was clearly a mistake on my part in not leaving enough space for notes.
=> PUT CONTACT INFORMATION ON EVERY PAGE. You never know when people will tear out a page or photocopy a single page of your handout. Putting your info on every page makes sure who ever sees any page of your handout can contact you.
=> PUT IMPORTANT RESOURCES ON EVERY PAGE. If you want people to keep your handout make sure each page has some important resource that an audience member cannot do without. When you put all there sources on one page it makes it easy for someone to tear it out and throw the rest of your handout away.
=> USE A TEAR OFF ACTION ITEM PAGE. Make it the last page so it's easy to tear off at the beginning of the seminar or speech. Havethe attendees use it for those special aha's they get. You can then have them say some of their items aloud which reinforces the value you are giving.