I've worked with several business partners and some were Great, while others not so much. The great ones were referred through my network of trusted individuals. Reaching out to people you know and trust and letting them know what you are doing and looking for is the best way to find a partner. The next step is to make sure you have shared values. Which means, you need to write down what your values are and then ask the potential business partner if they match with what his/hers are. That's the best approach I've found from my own experience.