If you are town, do not claim unless 1) someone claims your character and/or role, 2) you have night info that caught scum- example Swoosh claiming his info on Daboyle, 3) you are close to being lynched- example Matts claiming Xi when he was the leading vote getting D2
If you are town and claim a power role scum is likley to kill at some point, limiting the usefulness of the role
If you are town and claim a character/role with no night move, scum would have a better chance to hit/kill a power role because the pool is limited on the options by the claim
If you are scum, never claim that you are