I have certain advice I give to all landlords.
1. Always ask potential tenants to let you visit the place they are currently at. This way you can see how they are maintaining the unit they are in now. Either they'll let you or they won't. If not, there is a reason. If they say okay and then keep cancelling, there is a reason.
2. Try to contact the previous landlord to they one they have now. A bad tenant may get a good recommendation if this landlord is just trying to get them out of their place. The previous landlord may be more truthful with you.
3. Ensure your lease states that you will do regular walk-through inspections of the unit. You may decide after the first couple that you won't have to do them as often, but if there are damages being caused, you may be able to take care of it before it turns into something major.
Some management companies are really good, however, none of them are going to care about your property like you do.
Hope this helps.