Here's a very useful and informative article on pruning from your City's Urban Forestry Program:
http://www.ci.vancouver.wa.us/parks-recreation/parks_trails/urban_forestry/pruning-brochure.pdf
Note: To view this article, you will need Adobe Acrobat or the (FREE) Adobe Acrobat Reader program installed on your computer. If you don't already have it, you can download the free Acrobat Reader at: http://www.adobe.com/products/acrobat/readstep2.html.
Do you want even more information on tree care and pruning? Check out the National Arbor Day Foundation website at: http://www.arborday.org/trees/nineThings.html.