I like this site: http://www.dishpointer.com. Enter your address, select the satellite you want to point to and hit the "Go" button. It brings up a satellite view of your neighborhood with the site-line to the selected satellite. Zoom-in and then drag the little satellite glyph to the location of the dish on your house.
This will give you a pretty-good idea of where to point. I use references to the neighbor's house, landscaping, trees, etc. to know approximately how to position the dish once outside. Then it's a matter of hunting and fine-tuning.
Good luck.