That is the golden question. While a one-size-fits-all answer doesn't exist, there are a few common traits that can help your business succeed. Major topics of consideration include:
Market demand. It doesn't matter how great your product is if no one wants to buy it. While some smart marketers have been able to "create demand," it is difficult. It is much easier to fulfill a need than to try to make people believe they have one.
Cash flow. Capital can help your business stay afloat during challenging times, and it can help you to be able to provide your product and services when they are in demand. You'll need savings and/or a line of credit to help you succeed.
Hard work and energy. Simple "get up and go" is needed to make your business successful. When you run your own business, you'll need to wear many hats, seek your own clients, and manage sales to succeed.
Support from others. You'll need support from your business partners, employees, family and friends, customers and clients, and your network to help you succeed. If you do not have a network, you may want to start building one.