How little do you want to spend?
Do you want an earphone jack (I listen to mine, while in bed; therefore; essential).
Is the display "dimmable"? (as above).
When and for how long do you want to listen to it for?
I listen to the radio every night in bed, with in-ear earphones.
So here are my observations (Bush DAB radio, bought probably solely because it was the only reasonably-priced one at the time with an earphone jack, in the shop):
display is not dimmable - therefore I put a folded tee-shirt over it (so as not to have the bedroom lit up, all night);
doesn't have a volume "knob", only "up" and "down" buttons. Being fussy perhaps, but the first increment of volume is a bit too loud to be honest - a volume knob would be better;
when it is on, it emits a humming noise - very quiet, but noticeable at night (which is precisely when it is on) - annoying.