Find

To change every directory to have ug+rwx and sticky:

find . -type d -print0 | xargs -0 chmod 1770

-print0 and -0 are to deal with spaces in the filenames.

For read/write but NOT execute on normal files:

find . -type f -print0 | xargs -0 chmod 0660

To delete old files (e.g. older than one day):

find . -mtime +1 -exec rm {} \;