Sell vs Hold decision

[Robert Dean]

I'm just getting started.  Buying my first duplex this month.  Yes, I'm very excited.  

My business model includes buy, rehab, and then either sell or hold. In general, bigger and more expensive properties will go on MLS to sell, and I'll hold smaller and multi-family properties.

For others who do this, what attributes do you consider when deciding whether to hold or to sell?  Is there an analysis tool or combination of tools that you use to make this decision?