To add to what @Jonathan Greene wrote:1) Understanding the local market, so you know what Neighborhood Class your building is located in, what Class your Building is (condition & amenities), and what corresponding class of tenants will be attracted.2) Using all this data to properly set your expectations and a realistic ROI.3) How to better screen prospective tenants, including catching fraud, so your property performs better.

when you know how to run numbers and Data. 

Engaging with online communities such as BiggerPockets can also help you learn from experienced investors and explore different strategies.

Have you looked at AirDna or another STR data tool to obtain expected ADR?

I like the Share Group for skip tracing, its not cheap, but great data is worth gold.

You can't judge an area solely on crime rate and employment and salary data, but it certainly helps.

Regularly review your property's performance, and if the ROE dips, explore ways to extract and reinvest the equity to maintain your investment momentum. 

Then, you'd use the data on Airman or similar services to determine whether the metrics fit with your personal investment/return objectives.

I spent the last three weeks scraping data on this very topic. 

If there's a hole, it may be a red flag.b) sensitivity analysis: I examine all the assumptions, and make sure I can live with the worst case scenarios.c) "Stall and see": if they are getting money over multiple years, and there is no penalty for investing later, I would usually wait so I get some real performance data, versus having to look at theoretical pro forma information.d) Recession stress test: I will not invest in anything, until I subject it to recession level stress and see if I can live with the result.