How to know that the domain that you found is worth anything?!

[frank]

I checked with spamzilla there isn't anything saying drops or redirects. What are they exactly called?

And also are there anything else that I should be aware of?

Check score, redirects or drops followed by the letters SZ.

And these are pretty much it. 95% cases are covered by these basics. You don't need to worry about anything else.