The first test you perform when switching something on is the “smoke test” – literally you are seeing if anything produces (magic) smoke when you apply power. This is the most costly moment in any project as a simple solder bridge can cause those $10 MOSFETs to fry and set you back a week in ordering replacement parts.
One useful thing to do is limit the current (as you should know it’s the amps that’ll get you, not the volts) when you first switch on. If you don’t have access to a current limiting bench supply the easiest way to do this is to put a light bulb in series with the device under test.
I do this a lot, and so the last time I went to the hardware store I collected together about $11 in parts to make a device that would help – a socket with a switch (a switch always beats yanking out the power cable when something starts to go wrong), a lamp holder, a case and some flex with a plug.
All you do is wire up the socket with the bulb in series with the live wire. Now the circuit will be current limited by the power rating of the bulb.
ie. A 25W bulb will only let 25/120 = 0.208 amps pass through the circuit – anything more and the bulb will burn out. A 40W bulb will allow 0.333 amps, and so on.
So start with a low value and work up. You will know when the circuit is drawing all the current it needs because the lamp will no longer glow. When a surge occurs the lamp will glow brighter.
Note: Light bulbs are not linear devices – their resistance increases as they get “hot” – so when this circuit is first switched on their will be a tiny inrush of maximum current – so it’s not an infallible system, but it’s sure better than having no limiting at all.