How to allocate time
I recently spoke with a founder who has a legal background. He told me that after 2 weeks of focused work, he had finally finished writing the Terms of Service docs for his startup. This is an extreme example of poor time allocation.¹ In the early stages, your objective should be to make a product that people really love and will pay you money for. A great founder should spend 95%+ of her time building and selling.
After this happened, I realized that this was an instance of something I've now seen many times. People have a natural desire to allocate time on subjects they are most familiar with. While for most jobs this is fine (if you're a lawyer you should mainly be doing legal work!), founders have to be careful. Since the only objective for early stage startups is to find PMF, almost all of your time should go towards building and selling, regardless of your background or interests.
The founders that have to be most careful are the ones that have no experience building or selling – most MBA grads, bankers, consultants, etc. For example, ex-consultants are likely to waste time creating the perfect pitch deck and ex-bankers are likely to waste time on revenue forecasts.
Technical founders and ex-sales founders have an advantage because they will naturally focus on half of what matters. But since you need both halves to succeed, don't forget to check your blindspots. In more cases than not, technical founders will underestimate sales and sales founders underestimate what a great product will do.
¹ There are exceptions in highly regulated industries. But even in those cases, you are better off hiring someone or working with a consultant.