Agree with all the previous comments. Referrals are key.
To filter the resumes, here's somethings you can look for:
- Past experience: are there any experiences he/she had that had similar rresponsibilities to what you're looking for?
- Cover/Motivational letter: if you have this, it might be your great asset in filtering through. Look at the motivations and the language they use and see if that reflects the person you're looking for (personality wise, language wise, etc). You might want to read more on how language reflects personality/motivations, etc.
- Interesting/extracurricular experiences: might reflect initiative, proactivity, solution oriented or any other skill/competence you're looking for
Obviously, the most important is to know what you're looking for when it comes to experience, hard skills and soft skills.
Then you can think about how this person would write/talk (for cover/motivational letter) and what kind of background you're looking for.
Again, based on resumes alone, it is a bit of gambling. You can have a great person writing a terrible resume or the other way around.
I hope these pointers help you.