So how do I pick my seat ?

Bicycle seat that is...

I've been doing a lot of bike commuting to work while I wait for the local
trails to melt and dry out. The seat on my commuter was terrible, so I
swapped my comfy seat off my Klein for temporary commuter use.

Now the trails are drying and I really need a comfy seat on both bikes. I
know seat fit is very personal, and I know what feels bad, but how do you
get to test out a bunch of seats to see what feels good without buying them
and riding them for a few days?

Case in point, this spring I rode some trails in Baja on rental hardtails.
For the first few miles I thought - Hey these stock Specialized seats are
great, I'll get one when I get home. However, after a few more miles I
found I didn't like it at all. I can see buying a seat and setting it up
for a test ride, then thinking it's fine. A day later (when no retailer in
their right mind would take it back) you find out it's really not a good fit
for you.

What's the trick?