If you could give one piece of advice to a person who as starting a busines TODAY, what would it be?

I have started journaling every day of my life as a business owner (I have missed a few here and there), but after each entry, I try to write a few sentences on what I learned for the day in hopes that someday I can pass the information on. I think the absolute first thing I would tell someone who was thinking about starting a business with a partner, would be to consider exactly who that person is to the core and in every aspect of their life. Consider how they organize their days--do they use a planner? Do they answer e-mails back quickly? Is their work ethic at the same intensity level as yours? What kind of family did they come from? What was their socio-economic status growing up? Are they generally overachievers?

I was too young and naive to think through all of this and the differences between my partner and I have caused many many issues.

What would your first piece of advice be?