Sit about
Sit and do nothing, especially when you should be working
Sit around
Sit idly, doing nothing
Sit back
Wait for something to happen without making any effort
Sit by
Not try to stop something
Sit down
To take a seat. Help someone to sit.
Sit for
Pose for an artist or photographer
Sit in
Occupy a building to protest about something
Sit in for
Take on someone's responsibilities while they are absent
Sit in on
Attend as an observer
Sit on
Be on a committee
Sit out
Not take part
Sit over
Eat or drink slowly
Sit through
Stay till the end of something dull
Sit up
Suddenly take notice or pay attention
Sit with
Reconcile different positions