Question
Hi there, Thanks for taking the time to answer this very general question.  (you sound like a very knowledgeable individual.) Here it goes.... I'll try to include as much info as possible.
We have a large L-shaped lot.  It is south facing and our hardiness zone is 6.  We just finished building a walk out deck that takes up about 1/4 of the lot.  The rest of our yard is bare!  (except for dead grass, a grape vine that grows along the east fence and another vine that grows out of the south west corner of the deck, oh, and a large dogwood that is against the corner of the house)
I realize it is late in the season to get anything going but I would love to pick up some plants (esp. perennials and or trees) to plant and enjoy for next season. We have no shade, expect in the p.m.
The goal: flowers, privacy/shade , maybe even a vegetable garden.
We have horrible clay soil.  
So my question is....where do I begin?  What is the procedure for starting to beautiful a  garden? Are there any reference materials that you know of for the "beginning yard builder?"
Thanks so much!!!!!! PS- I can send you a picture if that helps! THANK YOU THANK YOU THANK YOU

Answer
I took a day to think about this wide-ranging question, so sorry for the slow response.

A good general guide I use (even as a professional designer) is out local water company's guide, found at

http://tmwalandscapeguide.com/landscape_guide/interactive/index.php

We live in a zone 6/7 so most if not all of hte plant materials there will grow in your part of the country, too.

As far as the clay soil condition, I'd recommend lots of organic compost (leaf litter from the fall, or grass clippings - rotted first, of course) to improve water retaining ability.  Also, liberally add agricultural lime (ground up marble) to help with the soil chemistry end of things...but its only a temporary fix, as rain will eventually leach it all out.

vric.ucdavis.edu/veginfo/topics/soils/managingclay.pdf

Hope some of this helps ~M