If I had to boil down my best startup advice into a single sentence, I'd tell people:
"Build great products that solve important problems."
If you solve an important problem, people will try and pay for your product. Getting someone to pay for your product is the surest path to revenues.
Yet simply solving an important problem is not enough. You also have to build a great product.
Building a great product won't help you get money from your customer...but it does help you get money from new customers.
A customer who buys your product because you solve an important problem might not give it a second thought once it's installed.
But a customer who thinks you have a great product will tell his or her friends.
Your customer will be eager to share, not just because of gratitude, but because sharing your product will win the gratitude of his or her friends.
If you build a great product that solves an important problem, you'll be able to organically acquire paying customers--nothing could be a more direct path to startup success.