My best tip, if I could only give one, not only applies to a startup but also to life in general. The one trait I've seen universally in successful people is this: patience.
Sometimes it may take you many years to succeed, but if you keep at it, you will.
I'm going to steal from Covey's "Seven Habits of Highly Effective People" : Begin with the end in mind. Because without that focus, any tips that I could pass along would be useful only in the context of certain types of startup strategies and goals, and how you choose to define success. So you need to know what you want the outcome to be in starting the new company, both in terms of your personal rewards, and what you would want for the company (and it's people!). If you have co-founders, investors, etc, then make sure everyone shares the common goals you envision, and touch base as you progress to make sure everyone is still in sync!