What guidance would you give to a friend starting a business?

Hi everyone! 

January is synonymous with resolutions, from fitness to launching a business.  For those with the latter goal, it can often be overwhelming to get a company off the drawing board. 

With that in mind, what advice would you give to a friend who was starting a business?   

The inspiration for this topic came from a recent conversation that I had with a good friend. They have decided that 2020 is the year for launching their business.  Their dream is to turn their hobby into a successful company.  It's as exciting as it is frightening for them.  

Our conversation focused on the importance of being as prepared as possible before the launch.  We agreed that any available free time should be utilized for research and laying the groundwork.  It reminded me of an old college professor who would often say, "fail to prepare, prepare to fail."  

If your friend asked you for guidance on starting a business, would the direction be the same? Perhaps, there are other lessons that you feel entrepreneurs should know. I look forward to hearing the Community's insights and thoughts on this question!