@Selena Williams
If they apply right away, then there's nothing you can really do about it. You will get to see an great view of them and can decide about showing them the unit then. :)
When I list my property, I use the google doc, go to shorten URL and then paste the URL in the ad. I also state my criteria in the ad. This keeps people from being fussy since they know the expectations ahead of time. If you don't have the criteria at least, I would suggest adding it. It would keep people from feeling like they were "throwing away money" on an application if they get denied for something like an eviction (or any other criteria you have).
Also, no sob stories from anyone - don't bend at all and verify everything. People are amazing at concocting stories that make your heart bleed, but don't do it.
When you call previous landlords, ask them questions about their property that a friend may not know. I'd suggest looking the property up on tax records, then you can ask when they bought it (If they have a bunch of properties, they may not know exactly), ask what LLC owns it (if an LLC owns it), verify the mailing address on tax records (maybe give the street and ask for the number of the address), etc. Stuff that a potential tenant's friend likely doesn't know. :)
I hope you get the perfect, long-term tenants! :)