When to rack the wash/mash

[tracker0945]

There seems to be a bit of confusion as to the best time to rack a wash for clearing.
1) when the S.G. reaches 1.000 or less?
2) after the foam cap collapses?
3) after 3 days have passed?
4) when the airlock stops bubbling?
5) when the airlock bubbles slow down?
All of these have been quoted at various times.

What type of wash/mash do you do and when do you rack?