You really need to measure the available water in the stream head is how far it falls, If it didn't fall at all it would not be a creek, it would be a still pond. flow is how fast if falls, by using a weir (which i did mention before) you can calculate the amount of water running through in Gallons Per Minute. flow is determined by how fast the stream flows, this can be calculated by measuring how fast a buoyant object goes between two given points.
Google "weir" "head" "flow rate" "small hydropower" those alone will yield enough hits to keep you reading for a few days.
Without doing a total site survey I cannot give you a step by step guide on what you'd need,how to build a dam, if you even need it, or what would be the easiest and most efficient method of generating power from your stream. However it WILL NOT be enough to get you off the grid. The best thing to do is to reduce power consumption, it can be done, and no-one can tell me that a dishwasher is more efficient than hand washing. Just the electricity alone saved by washing by hand would save a lot, and no it does not use less water! Dish washing done right, can become a social activity.
I'm just betting I could walk around your house and in a 1/2 hour point out how to save at least 100 a month in electricity. It's called turn it off, unplug it, get rid of unneeded or seldom used "conveniences"
For instance, in my house there are two of us. I avg 32./mo on my electricity bill, I have 4 computers, an LCD HDTV, and quite a few other "modern" appliances such as a microwave. I also have a full shop of power tools which get used on a regular basis.
There a lot of guides on the internet on how to save on electricity, water useage and other costly items, let me tell you it is a LOT easier saving electricity (and cheaper in the long run) than generating it!
Remember people got along just fine without our modern conveniences before the advent of easily obtainable electricity,