The past tense of mind one's p's and q's is minded one's p's and q's.
The third-person singular simple present indicative form of mind one's p's and q's is minds one's p's and q's.
The present participle of mind one's p's and q's is minding one's p's and q's.
The past participle of mind one's p's and q's is minded one's p's and q's.