Question about CLUSTER

Hello,

I'm planning to cluster a few large tables in our database but I'm
unable to find any recommendations/documentation on best practices --
Mainly, whether it's better to use an index which has a higher idx_scan
value, a higher idx_tup_read value, or the higest idx_tup_fetch value.

I'm assuming that idx_tup_read would probably be the best choice, but
want to get other opinions before proceeding.

Can anyone point me to docs which explain this better?

-salman