Example CSS snippets referenced on my blog: http://donttrustthisguy.com/2010/03/07/the-art-and-zen-of-writing-css/

be_generic.css

/* The two rules below would accomplish the same thing. */
div#primary_content p {
   font-size: 0.875em;
}

p {
   font-size: 0.875em;
}

best_practices.css

/*  KEEP OUR CSS CLEAN
    Some guidelines to follow:
    1. Break code down into sections.
    2. Keep your rules alphabetically sorted.
    3. Only put one selector per line for a block of rules that apply to multiple selectors.
    4. Indent your rules, only one rule per line.
    5. Indent proprietary properties with two spaces. Keep these properties directly below the proposed property.
        
        example:
        
        element#id,
        element.class {
            rule1: value;
              -webkit-rule1: value;
              -moz-rule1: value;
            rule2: value;
            top: value;
        }
*/

nightmare.css

/* Over-specified selectors create a huge nightmare. */
.admin #content ul.form > li input[type="text"],
.admin #content ul.form > li input[type="submit"],
.admin #content ul.form > li textarea,
.admin #content ul.form > li select,
#content .standard_form ul.form > li input[type="text"],
#content .standard_form ul.form > li input[type="password"],
#content .standard_form ul.form > li input[type="submit"],
#content .standard_form ul.form > li textarea,
#content .standard_form ul.form > li select {
   border: 3px;
   padding: 2px 4px;
}

/* The most generic equivalent which accomplishes the same thing. */
input,
select,
textarea {
   border: 3px;
   padding: 2px 4px;   
}

/* We could gradually become more specific as we needed... */
.admin input,
.admin select,
.admin textarea {
   background: #333;
   color: #ccc;
}