While i agree with ThePiachu, here some additional thoughts.
- Pool software
- Beeing a solominer would create the need for a pool software. While very few are opensource, the majoritiy is proprietary.
- As a solominer youre solely responsible on your own for any serverside/softwareside security, dealing with ddos and exploit attempts. (However, i dont like to rely on others i barely know.)
- Pool owner
This is already mentioned, but highly important. Questions one should ask are:
What is the motivation of the pool owner to run the pool, how does he makes profit?
Has the pool owner been accused for scam or ben involved in other unethical behavour?
How are the coding skills, admin skills, security skills?
Is he running his own software?
Is it a team or one man business, if a team, how does the team profit without your coins?
- Payout & reward system.
Additional note: even as solominer you will be object for intrusion attempts (at least very likely), as bitcoin in its nature is transparent and will make your node appear to the public. (Diversify your bonds ;))