Once you have decidied where everything is going to be located, you should start and finish your "pre-wire" job. Always allow for extra length in you runs of cable.(you never know when you may need a bit more because of mistake or a last minute location change)Many people here on Audioholics.com use Bluejeanscable.com for all of their different cable and connector needs. There prices are very reasonable, and their customer service has always been great for me. There is also Monoprice.com for cables and connectors, and alot of members here use them too. I haven't used them yet myself but I have heard good things about them too.
Many people like to use wall plates to keep things nice and neat looking for their connections. I like to make my connections directly from the original cable each time. I feel that this method offers a better overall signal strength. Others may not share the same opinion, so this is something you will have to decide yourself.
Allow for proper ventilation before your set any equipment in place. Just take into account the dimensions of anything you plan to install and know it's heat charecteristics. Then go from there. I had a problem with my receiver at first because I was so consumed in how nice and neat and streamlined I wanted everything to look, that I left absolutely no room in my enclosure for ventilation or cooling of my receiver when I installed it at the very top of the enclosure. Needless to say, I had many issues at first. Everything was fixed later on, but all of the repeat work and Tylenol could have been avoided with some caredul planning beforehand.
I am sure there are alot of other things that need to be addressed, and you should get alot of help on this site once you give all of the particulars on your project.(room dimensions, Gear,WAF,etc..)I wish you luck and success on your project(s).

Joe B.