Being able to design your way out of a wet paper bag is one of those skills that is immensely useful as an entrepreneur. Not everyone has an awesome designer as a cofounder and, let's face it, a great many people who are technology wizards or business experts suck at producing something that looks even half-decent.
And yet, decent design is not magic. Great design might be out of the reach of those who don't have a knack for it (though it's worth mentioning that this knack tends to be acquired through decades of practice, not magic), but decent design is within everyone's reach.
Here, then, is an excellent guide to the basics of design. Enjoy.