Just talked to a freind today on a visit about this very topic. The absolute first think to do is figure out what all you want to be able to power and add up the total wattage. This is the number you need to base your system on. I would also allow for 10-20% extra to make up for losses due to line loss of the length of your wiring run and ineffeceintes of your system. My buddy showed me a months worth of testing he performed with one of his panels. I was surprised how little it provided. He took cloud cover, snow cover, and other things into account and did a hour by hour comparison. On cloudy or partly cloudy days there was hours that he got little to nothing out of the panel. Tracking the sun is also a important factor. I would be surprised if you couldn't increase your output by 30% or more by doing this.
I'm looking into this for a couple of smaller uses and will be doing research on this myself. One item to check out is called "Kill A Watt". It plugs between the electric outlet and whatever your are powering. It measures many different things over a period of time that will provide information you need to build your system. Also check out "Home Power" magazine, which also is available on line. They discuss all alternative energy options and have ad with web links for many different solar providers.
Greater love hath no man than this, That a man lay down his life for a friend.