1. Look at the product. Can you describe what it is, what value it creates for customers? Is it exciting? It probably shouldn't be. In 9 out of 10 cases boring products in boring industries will lead to steady work and chance to add real value to the company, get raises, etc. Small company unicorns can raise money, but they don't last. Successful companies ship products and create happy customers.
2. You want a company that is high trust with their team - including in interviews. How many customers do they have? What is their runway? How much money do they make? What are the biggest complaints from customers? Do they have any raving fans, what do they say? Who are the dominant personalities in the business, who leads? If the company isn't willing to go into detail even over the phone on this stuff then tred carefully.
3. Read! Don't give up an being business-savvy. There are a lot of good online lectures, tons of great books, podcasts, etc. You don't need to be an expert to start to develop a nose for what is going on. Listen or read something once a day and you'll gather the tools, vocabulary, and emotional perceptions to ask better questions and even help companies execute their strategies. Believe me, having a developer who cares about product, customer, and execution even half as much as they care about code can be the difference between life and death for a small company.
Entreleadership (good, easy book on leadership and business):
Tropical MBA Podcast (will touch on sales, product, marketing, teams, and more):
Gimlet Startup Podcast (start with Episode 1 to go behind the scenes of what the business leaders are feeling):
Harvard Business School Youtube Channel: