Conditions vary
When operating a glider towplane out of a dirt field with no hard pad to do run-ups on, we used to do a rolling mag check on the AM warm-up flight. Any stationary run-up on that airport would result in lots of rock chips in the prop.
So for the first flight of the day, roll out of the tie down, keep moving, when on centerline of the runway, go to 2100 rpm, and while accelerating, reach over and do a mag check. Then, apply full power and continue the takeoff.
An observer watching this first flight of the day might very well assume that no mag check was done. (unless they had keen ears and made a point to listen).
Out here in the west, with drier climates, condensation in tanks is extremely unlikely. How many times have I left the tanks 1/4 full for weeks, and then sump-checked the tanks and found nothing. Enough times that I can tell you with absolute certainty that if I sump-checked the tanks last night, they are safe to fly this morning.
If I gave the plane a bath last night at the wash rack, I fully expect to find a little water this morning. Otherwise....no.
I tailor my pre-flight to my knowledge and understanding of the airplane:
A rental or club plane gets an extremely thorough going over. I have found unreported damage from the previous user - the result of hitting a wingtip on a post during landing roll-out. I once pre-flighted a glider that was fairly new to the fleet (it had been flying for about two weeks). When I moved the controls, it seemed like the ailerons were kind of sloppy to me. So I pulled out the seat and stuck my head way in the back. I found a castellated nut sitting on the gear well, a washer hanging by the last thread, and an AN bolt backed half way out of the aileron bell crank connection. I walked into the shop, grabbed a wrench and a cotter pin, and ten minutes later I was on tow. The funny/scary thing? After properly installing that control linkage bolt, the aileron slop felt exactly the same. Had I been a bit more familiar with the airplane, I would have dismissed it.
My own airplane, I'm looking for things that seem out of place, anything changed. I once checked the oil on my Citabria and noticed a small puddle of oil under the cowl cooling exit. Now if I were unfamiliar with the airplane, I would probably have asked the line crew if that airplane was known to leak a little oil. But it was my airplane and I knew it did not leak oil. So I pulled the cowl off. Following the oil trail to its source, the oil pressure gauge tap in the block, I grabbed the fitting and gave it a wiggle. It broke off in my hand.
What I don't do is inspect things that have not changed in 500 hrs, were fine at last condition inspection, and I am certain are still fine. I don't wiggle my control surfaces for slop in the hinges at every preflight. Such slop would take time to develop, not something that is going to change overnight. I don't look at every Nylock nut on every control hinge. Because they were installed 500 hrs ago with fresh nuts, torqued properly, and have not changed. Have you EVER found a Nylock nut that was properly assembled actually come loose? Perhaps one that is on something that is periodically disassembled and has been on and off multiple times. Not a hinge bolt.
What I do check EVERY time:
(1) The jam nuts on the rod-bearing hinges.
(2) the plastic clevis fork on the trim tab. (I wouldn't check regularly if it was metal. I think this plastic part is a vulnerability.)
(3) fuel state
(4) oil state
(5) propeller surfaces
(6) pitot tube and fuel vents for foreign (or domestic) obstructions
(7) air in the tires
(8) listen and look as I pull the plane out of the hangar for anything unusual
(9) mag check
(10) prop cycled
(11) controls free
Numbers 1--5 can be done the night before. If I skipped (7), I sure would notice it during (8). It is an interesting observation that a locked hangar isn't a guarantee of fuel state from the night before. I will change my attitude and procedure on that based on this discussion. Its not impossible that someone could steal fuel overnight. Would I notice it on my fuel gages and EMS? I think so, but not positive. So....I'll check the tanks in the morning from now on. Thanks.