Include a background graphic by using background="file".
Keep your background file small and do not choose a pattern that makes reading the text difficult. Also realize that people will view your background at different resolutions. In order for a background not to repeat horizontally on higher resolutions it should be at least 1,200 pixels wide. A left margin that repeats and obscures text will definitely detract from your site.
Set the background color by including bgcolor=#rrggbb.
If you use a background graphic, your background color should approximate the color of the graphic to make your text readable in case the background graphic does not load.
Set the color of your text with text=#rrggbb.
Set the color of your links with link=#rrggbb.
Set the color of your visited links with vlink=#rrggbb.
Your text, link and visited link colors should be easy to read against your background.
An example of a <body> tag with all of the above:
<body background="./gfx/back.gif" bgcolor=#dcc4ac text=#6c2c14 link=#006600 vlink=#a00000>