Bill replied:

There are repeater location maps and location searches at http://www.tropinet.com/radio/repeaters.html

Bob replied:

Colin, I guess you're new to UHF so I'll just run through the basics.
Just go through channels 1-9 and press the transmit button for each. If there is a repeater in range you will get a brief signal immediately after releasing the button. You won't hear anything but the signal strength meter will register a brief incoming signal. Alternately, repeaters transmit their call sign in morse code at intervals. If your radio is scanning it will pick these up. You've chosen the right brand!! I have the "top of the range" - the TX 4400 and it's a great set - out performs everything else on the market and I get some amazing distances with it!! The extra 20 channels on the TX 4400 (41-60) are the "cream on the cake" as they cover most police and emergency services ... and even some taxi and bus services in country areas.

AC replied:

Bob its channels 1-8. You will not recieve a response from a repeater if your radio is in simplex mode (after a transmission). To access a repeater yor radio must be in duplex mode. As along as your in range you will always hear the repeater no matter what mode you are in. But like Bob said scanning is the best way to tell.