They have a pH meter which includes a reader and a stick that's very
easy to use for $24.99. They also have a kit that'll check the pH,
nitrogen levels and several other elements.

We got a soil pH meter, a Kelway HB-2. This is a cone-shaped device
(no electronics or batteries, has an analog guage) which you clean
with a conditioning film and put into the soil. The needle is
supposed to deflect and then slowly approach the real pH. The soil
needs to be quite wet (we've not gotten a reading, at least this
summer, without adding water, which I guess is OK if we use rain water
rather than tap water).

So I guess this is working but I find it a bit hard to be confident
that I'm using it right and can believe the results. If other people
are using other soil test kits, I'd be interested in hearing about it.
I like the idea of working from knowledge rather than guesswork. But
I'm not sure what method is best. I'm assuming that the soil is
different in each of the beds (given previous owners amending the
soil, growing different plants, throwing potted plants in the beds,
etc, etc), which makes me a little uncertain whether "just send in the
soil for a soil test" is the right answer.