Avoid, or if need business dispute an once of prevention is better than a pound of cure.

The governing document must protect you. Ideally, you should prepare a single document titled "Agreement", or something similar. Both you and your counterpart should sign it at the beginning of your relationship.

If you do not have that document, seek to create it, in co-operation, with your counterpart. Do that when the relationship is positive.

Without these steps, you may still have an agreement. For example, an exchange of emails or text messages between you and your counterpart. However, whether this forms an agreement can be a complex question, and varies from case to case. Further, such exchanges are often only considered once the relationship has soured.

BE CAREFUL WHAT YOU SIGN OR WRITE!