Don't give them a chence to develop dis-taste about you.
Dogs do this all the time. In any decent dog park, dogs run with friends only. And how they figure out who's friend who's not? -- Actually with just a simple trick: smell! When the encounter at the first time, they smell each other all the way down, from the mouth, to other parts immediately down, and finally the private hole, and if all smells about right, then they become friends and hang around together pretty happily, and productively.