If you want one that will get the most frequencies for police,fire,etc...
Find one that offers trunked frequencies, or a trunking scanner.
Google it
You can find most local police and fire dept frequencies online with a few searches, trunking scanners will give you frequencies that major metro cities use like frisco.
You can alsop find live streaming scanners online on different sites.
I keep a scanner around pre programmed with all the bay area frq's, you can hear some interesting shit going on out there, and get a headstart if its involving you
The radio shack pro series (pro-51, pro74, etc) are some one the easiesr and more reilable one, you can also buy chips for these to get additional frequencies.
Stayin one step ahead is just part of the game