6v6gt:
TVS diodes can protect against spikes.
A polyfuse, then a diode reversed after it across the supply can protect against false polarity.
But a search using those terms in the forum will show other ideas.
Sounds good about the TVS diode between where should I connect it and which should I get?
And how'd you mount the diode? wouldn't it create a too high of a voltage drop if you put it in series?