Ensure that you are legal.
Still pictures from fixed wing is one thing... but motion picture work ie video puts extra demands on the pilot. Most DSLRs shoot video so make sure before you take off, if the photographer want to turn into a cameraman mid flight...
The issues are low and slow to keep the shot wide and steady. Also trying to do a perfect orbit despite a wind and slide slipping near the stall.
Excluding war zones, aerial filming kills more cameramen than all other filming activities combined. The pilot usually doesn't come out without a scratch either... two professional cameramen killed in fixed wings this year.. along with their pilots.
Home made harnesses have caused the death of at least three aerial cameramen following a controlled ditching, where all others survived, the cameramen have drowned.
Mickjoebill