Check with your department to see if they use the SIRS form, an alternative department form or both. Follow the procedure for collecting the evaluations outlined by your department when using its instrument. You can supplement the feedback you receive from the SIRS or Departmental evaluations by developing alternative evaluations. Instructors can request written or verbal feedback. You might have students evaluate you as part of an assignment or on a form you have generated.
Evaluations can serve many purposes.
You can distribute them or request comments at any time during the semester. This text proposes techniques which are more informal than SIRS forms or departmental forms. Each department has different policies concerning supervision and evaluation of teaching assistants. You should check with your department or supervising faculty member to find out what kind of evaluations will be done of your teaching performance. Beyond that, it is your right to request a faculty visit or a visit by another TA who can give you feedback.