Get with an experienced, local real estate attorney to draft not only your lease, but application and lawful tenant criteria. We always provide a criteria and application up front (before showing) and it weeds out anyone that would attempt to waste my time.
I discriminate against falsified information, unverifiable identity, negative feedback from prior landlord(s), unqualified types of income, not enough income, unpaid judgments, evictions, certain criminal convictions and a history of poor money management resulting in late payments. These disqualifying categories are not mutually exclusive, so any combination can be used to reject an applicant.
Immutable physical attributes or disabilities do not concern me.
As far as Service and ES animals go, If the accommodation is reasonable, there is a verified disability, the animal is, in fact, needed, the animal is taken care of medically and there's a proven nexus between the individual and animal then I see no problem. Any area that has a huge swath of ESA abusers will eventually see an upward pressure on rents anyway.