The best way to avoid and/or resolve disputes early is to make sure you have good communication with the person(s)/businesses in which you are dealing. If there is any uncertainty, clarify at the earliest possible time. And, make sure you document the transaction (i.e. emails/invoices/receipts/work orders) and save or back up your documentation.
This information will be well worth the effort in case you do have a dispute, because you will have the evidence to support your position. Bring another person (i.e. witness) to discuss the matter with the person you’re having a dispute with and/or bring in a neutral person who can might be able to mediate the dispute. Avoiding and/or settling disputes early will save you from unnecessary stress and money in the long run.