This will depend on the type of business you are running.
If you will be providing confidential information to other individuals or entities, you will need non-disclosure agreements.
If your business purchases goods or services from third parties, you will need vendor and services agreements.
If you sell goods or services to customers, you will require a sales agreement.
If you sell products directly to consumers, you will need a return policy.
If you are licensing out or licensing in intellectual property, you will need an intellectual property licensing agreement.
If your business has an online presence, you will need website terms of service and a privacy policy.
If you have employees or work with independent contractors, you will need agreements in place with these individuals.
In addition to the contracts you put in place, you will likely be presented contracts by other parties you work with, and a business contracts lawyer can review these contracts on your behalf.