You probably only want to monitor the 700mhz system since that is what the city is moving to. The 800mhz system will eventually not be in use, and already doesn't have all the traffic on it. Unfortunately the scanner you have doesn't fully support the 700mhz system, it will sound like it is getting interference at times, but you can adjust the P25 levels, antennas, and location to try to help this. I have the same scanner I use around the house and it works well enough, but has trouble when in my car on my mobile antenna depending where I am. My feeds are provided by SDRs that support the 700 simulcast system.
For Fire, you want to listen to the dispatch channel to find out what is going on, they will read out a dispatch and give the Command and Tac channels. You want to then move over to that command or tac channel. For instance, the dispatch could say "Structure Fire, 8 Alpha 8 Bravo" 8A is the command, 8B is the tac.
For PD, you want to listen to the divisions that are near you. There is often too much going on to listen to every PD dispatch. Here is a beat map, figure out what areas (colors) you want to listen to and lock out the rest:
The 325P2 has a temporary lockout feature, you can hit LO and that channel will not come back until you turn the scanner off and back on again. The way I have my banks sorted in the scanner are the top row is PD, second row is Fire, third row is Misc.
1 - PD Disp North divisions
2 - PD Disp South divisions
3 - PD Tacs/Misc
4 - FD Disp
5 - FD Commands
6 - FD Tacs
7 - Lifeguards
I turn on and off the banks I want to listen to, and then use the LO button to silence the talkgroups I don't want to hear within those banks if something gets busy on one of them. Generally I will keep the PD Dispatch for whatever part of town I am in (North or South) and the FD Dispatch banks active. Then as things happen I will turn on and off the banks to target what I want to listen to. So if I have bank 1 on listening to Northern, Eastern, Western and Mid City dispatches, and something crazy happens on Eastern, I will just hit the temp lockout button whenever a different dispatch channel comes up. Then when that call is done I will turn the scanner off and back on so it clears all the temp lockouts and goes back to scanning everything. If I hear an interesting Fire dispatch I will turn on the Command bank and lock out anything that wasn't given during the initial dispatch so I only hear that call I am interested in. I may turn off the PD Dispatch if I only want to hear the fire calls as well. You will just have to use it for a while to decide how much you want to hear at once. If once scanner isn't enough you can get more and listen to PD North on one and PD South on another and FD on a third if you need.
wiki.radioreference.com
