The most effective solution is getting good tenants in the first place. Screen each and every potential tenant for credit history, criminal convictions, and evictions. Set your application standards and stick to them (i.e., don’t fall for any “hard luck” stories). There are certain restrictions on what may be considered in the evaluation process, so consult an attorney on the specifics. (NOTE: If you charge an application fee, you must provide applicants with written notice of your screening criteria, the amount of the screening charge, your application process, and the applicant’s right to dispute the accuracy of any reported information.)
After you approve an application, make sure that the tenant signs a written rental agreement, rules, and any other rental documents before taking possession of the rental unit. While it is possible to establish a tenancy without any rental documents, it is always more difficult to handle potential disputes without written documentation. Don’t agree to any “informal” tenancy arrangements – they typically lead to disputes.
After the tenancy begins, be responsive to any complaints by the tenant concerning the condition of the rental. For example, send a handyman or contractor over to inspect and/or repair any complaints made by the tenant. While there are limits on what constitutes a “habitability” issue affecting the actual livability of the rental, err on the side of making repairs unless the repair issues become unreasonable.
Finally, treat your rental like the business that it is. If rent is due on the 1st of the month, then issue 72-hour nonpayment notices on the 8th of the month when rent is late, as allowed by Oregon law. Address tenancy problems (i.e., unauthorized occupants, pets, maintenance issues, etc.) as soon as you learn of them. While it might not be possible to avoid all tenant disputes, addressing problems as soon as they arise will greatly improve your legal position if you end up in court.