Easy as pie. Really. Just go buy any kind of cheap automotive spark plug.
Bend the electrode with a pair of pliers as jim beam says. Pull the easiest
plug wire you can find from its plug, and insert the plug in the plug wire.

Touch the plug to any ground (valve cover bolt, battery negative terminal,
etc). Now have a friend crank the engine. If you're getting spark, it will
be loud and yellow.

If you're worried about getting electrocuted, don't. If you do happen to
get a shock, it does absolutely *no* harm at all. It just startles you.

Actually, you don't even need a spare plug. Just hold the empty plug wire
close to a ground (any bare metal part on the engine) about 1/4" or 1/2"
away. Then have your friend crank for a second or two.

DO NOT allow the car to start with the plug wire removed! If it should
happen to start, shut it down immediately to protect the ignition coil.

Good news,  I followed the steps below and felt every click. So the main
relay is ruled out. Also tried the off-on x 6, the engine did not start.

The last reco is a little out of my league, I think I'd need more docs about
plugs and sparks before attempting that.

Not necessarily. All it means is that the fuel pump is running for two
seconds.

Reach behind the dash so you can feel the Main Relay.
Turn the ignition to ON (not START)
There should be a click as the Check Engine light goes on, then anoher as
it goes off. You will hear the pump run for two seconds.
Turn the key to START. At that point you should feel a THIRD click.

If you feel all those clicks, the Main Relay is OK. If any clicks are
missing, the Main Relay has a cracked solder problem.

If the Main Relay is OK, turn the key to ON, wait for the Check Engine
light to go off, then turn the key to OFF again. Quickly repeat a half-
dozen times or so. If it now starts, the fuel pump check valve is bad,
allowing pressure to bleed off.

If it still does not start, check for spark as you crank. Buy a cheap spark
plug at the store (doesn't matter what kind), pull one of the plug wires,
insert the new plug, hold the hex part against a ground, then watch the gap
as somebody cranks. Any spark?

When I turn the key to position 2, I hear a soft ~2-second whir which is
probably the pump, followed by a non-start. By your logic, that means the
main relay IS working OK, since I didn't need to slap the dashboard...?  :)

My timing belts are probably 15,000 miles old so they should be healthy.

Thanks for the helpful ideas.

=============================

You dont' even have to touch it to prove if it's causing the problem. In
a quiet place, turn the key to position II. Listen to fuel pump run for
2 seconds. If it doesn't run, smack the dash and listen. If pump runs,
it's your Main Relay. You car will now start, and the vibration will
keep the relay working until you shut the engine off.

Have you checked that that your timing belt isn't broken yet?

'Curly'

In an earlier thread (1994 Honda Civic won't start) people recommended
that I check the main relay to rule out a failed solder connection (for
example http://www.tegger.com/hondafaq/mainrelay.html).

Would it suffice to simply touch up the existing connections with the
tip of a soldering iron?

Looking for an easier workaround than re/desoldering just to rule out
this simple part...

Thanks.