Not the big decisions. The small ones that nobody thinks about until they are a problem.
1. Parking. Tell people where to go before they leave home. In most buildings this causes more friction than everything else combined.
2. A reachable power socket near wherever the musicians sit. Not across the room, not behind a sofa.
3. The doorbell. Mute it after the start time and put a note on the door. Otherwise it rings through the quietest bhajan of the evening.
4. The ceiling fan directly above the performers. It interferes with voices and with hand percussion, and nobody thinks to switch it off.
5. Water, refilled. Warm room, long set. One bottle at the start is not enough.
6. Somewhere to put instrument cases that is not the middle of the walkway.
7. Neighbours. A word beforehand prevents almost every complaint. This matters more in older buildings than new ones.
8. A real start time. If you want music at seven, invite people for half six. Everyone knows this and almost nobody does it.
9. The kitchen. Close it during the set. Extractor fans and fridges are much louder than they seem once a room goes quiet.
10. Prasad timing. After the music, not during. Plates and singing do not combine, and serving mid-set empties the room.
11. Light on the musicians. Not a spotlight, just enough to see faces. Rooms where the performers are in shadow listen politely; rooms where they can be seen join in.
12. Somebody who can make a decision. At a family gathering this is obvious. At a society or office event it frequently is not, and an evening can stall for twenty minutes because nobody present is sure whether they are allowed to move the chairs.
None of these cost anything. All of them are easier to sort out the day before than on the night.