- double faults and not communicating strategy are my biggest mistakes...
- using drop shots is a mistake i make as well. very effective in singles, not effective in doubles.
- remembering how big the court is for angles hit from the baseline. i tend to be restricted by a singles mentality.
Disclaimer: I'm NOT a coach...
Real tennis: https://www.youtube.com/watch?v=yDqnkLJ9BtM