He should pin up a planning notice on his gate or close vicinity where Joe public can read it, detailing what he has applied for,with an address to contact if you have any objections.
All objections should be submitted in writing to the relevant authority, stating the reason for the objection
Alternatively you can look at the local authorities web page and do the same there, that's what we did,and the chap has had to demolish,as he was building without consent