First of all, I would strongly recommend you hire a realtor to help you. I do not know how rentals are done in Pennsylvania, but here in Northern New Jersey it's a no brainer. It is customary here to ask the tenant to pay the realtors' fee so there is no downside whatsoever.
However, whether you hire a professional or decide to do this on your own, these are a few things you should do to ensure you find a good, highly qualified tenant:
1. Do a complete background check including credit history, criminal history and eviction history. I can recommend web services for this if you contact me here on Trulia.
2. Get employment and income verification
3. Get and CHECK references.
4. Insist on BANK CHECKS for the security deposit and the first month's rent and, if applicable, the realtors' fee.
5. Do NOT give them the keys until all the above has been satisfied.
6. If ANY red flags are raised, just walk away.
I once got scammed by a young lady who falsified employment information (said she owned the business), income tax returns, and bank account statements, then said she didn't have time to get bank checks. The landlord was so anxious to find a tenant that he agreed, against my advice, to accept her personal check, and of course everything bounced! It took him three months to evict her for one reason or another (she had kids and kept leading him on and tugging at his heartstrings) and ended up in jail on because the combined total of the bad checks was so high it was a felony and not a misdemeanor. What a night mare! Never Again!
You know what they say, "Fool me once shame on you, fool me twice shame on ME." And, in the words of George W. Bush, "You won't fool me again!" LOL! Now, whenever a landlord wants to compromise I tell them this story. Yes, it is an extreme example of what can happen, but if a tenant gives you a hard time before they are even in the door, what can you expect once they take occupancy? Better to say, this is what I require, take it or leave it.
If you take these measures, and do not compromise on your criteria, you will have the best chance of finding good tenants so you have very few problems in the future.