1. Google Page rank – The higher the better
2. Alexa traffic rank – Better ranking is good.
3. Alexa – Check on how the site looks in the past.
4. Is it under cash parking? How long? The shorter period of time is better choice.
5. Check existing backlinks (The more is the better)
6. Search in google and yahoo on the domain name and see the related results in the past. If it has more scam results, beware.
7. The age of the domain (The longer history is the better choice)
8. The estimated value, daily revenue and daily page views analysis (The estimate value is just a guidance – most of the time, it is overvalued)
If you have any additional points, please feel free to share it here.