Gday Jared , welcome to the group. Setting frequencies to a channel number is totally up to you mate , there arent really any rules there. I just set mine up so i roughly know where to look when i wanna find something quick, for example i have aviation frequencies in the first 20 channels, then police in the next 20, then firies and SJA next, etc etc...you get the picture.
The best advice i can give you for finding local frequencies is to use the following link
http://web.acma.gov.au/pls/radcom/regis ... .main_page
This is a government website that shows all licensed radio frequencies in the country. When you get to that page you will find 3 drop down boxes near the top of the page. Change the left hand box so it says sites, leave the middle one to say any detail and then enter Rockingham in the right hand box. So now it says " find sites where any detail matches Rockingham". When you click on the Go button you will be taken to another page with a bunch of local addresses on it. On the right hand side of the addresses is the Site ID numbers in blue, click on these to get the expanded details for that site. What you are looking for in these details is the following information.... Where it says operating mode you want it to say Transmit and where it says coverage you want it to say Local. If the information matches these details this means you should be able to receive transmissions from this station when in the Rocky area and you can now enter the assigned frequency in you scanner.
Sorry if i made your head hurt

but go have a play with that and im sure it will all make sense to you soon.
If you dont have a copy of the instruction booklet for your scanner, here is a link for it
http://www.uniden.com.au/RESOURCES_MAIN ... or_web.pdf
Any more questions after all that .....just ask away.