This page has moved. It can be found @ Ilona’s Garden: 5 Tips To Improve Clay Soil, along with other informative posts on soil improvement.
But if you want only one really important tip for working with clay soil, it is this:
Don’t work (dig, hoe, rake, step on, etc) clay soils when they are saturated with moisture (WET)!
You can find out ways to improve a clay soil by following the link… but basically not working these soils when they are wet is single most important thing you can remember.
However, do go to the article mentioned to get really helpful hints if you have this soil condition in your garden.