The metrics you provided, as well what Scott suggested work well. Figuring out the market first will give you a better idea of what your Cap rate should be, what per unit cost is around, rent rolls, and the like. Also if you are able to see a general trend of the area, such as gentrification or increasing market rents it is a good area to buy into.
Once you have these numbers, then you can start analyzing individual properties. Drive around their area, obtain rent rolls, talk to tenants. You can use a simple + or - sliding scale to determine if the property should be looked into more:
+: is it around public transit? (BART or Ace train for the Bay Area)
+: below market rents
+: minor/cosmetic deferred maintenance
OR
-: bad surrounding neighborhood
-: next to an airport/factory/noise pollution.
etc.
There are many books around this topic, and I suggest "How To Buy & Sell Apartment Complexes" by Steve Vollusci if you haven't read it already. Good luck investing!