I decided to embark on the entrepreneurial journey over 20 years ago ... and haven't looked back. I love what I do, but being an entrepreneur isn't for everyone. The first two things you should do is (1) make sure that those who share your life with you are on board and (2) make sure that being an entrepreneur is really what you want.
Once you've checked off these two items, then I recommend looking at your business from the outside first and gradually looking inward. Here's a list of priorities:
1. Your Customers - no company is successful without customers. So, as a startup, you need to know (1) who are your customers, (2) how do you reach those customers, (3) how much are those customers willing to pay.
2. Your Team - determine the personnel gaps that need to be filled and have a plan to fill those gaps. These don't have to be employees. You may be able to fill some gaps with contractors, consultants, advisors, etc.
3. Your Business - determine your corporate structure and file the appropriate registrations. Now is the time to make sure you separate business from personal.