Like many I tend to come across ie6 rendering bugs and like many have developed my own (read others) set of techniques to overcome theme.

Correct doctype, with full correct DTD, transitional or strict (solves so many issues without having to change anything):

< !DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">

Reset stylesheet (via Eric Meyer) the goal of a reset stylesheet is “to reduce browser inconsistencies” see here for a deeper explanation, again solves many many issues and enables a new build to start from the same starting point on every browser by resetting common element behaviour.

/*
=Reset
*/
html,body,div,span,applet,object,iframe,
h1,h2,h3,h4,h5,h6,p,blockquote,pre,
a,abbr,acronym,address,big,cite,code,
del,dfn,em,font,img,ins,kbd,q,s,samp,
small,strike,strong,sub,sup,tt,var,
dl,dt,dd,ol,ul,li,
fieldset,form,label,legend,
table,caption,tbody,tfoot,thead,tr,th,td
{margin:0;padding:0;border:0;outline:0;font-weight:inherit;
font-style:inherit;font-size:100%;font-family:inherit;
vertical-align:baseline;}
/* remember to define focus styles! */
:focus{outline:0;}
body{line-height:1;}
ol,ul{list-style:none;}
/* tables still need 'cellspacing="0"' in the markup */
table{border-collapse:separate;border-spacing:0;}
caption,th,td{text-align:left;font-weight:normal;}
blockquote:before,blockquote:after,
q:before,q:after{content:"";}
blockquote,q{quotes:"" "";}

And some other fixes I have picked up

/* -------------------- */
/* =IE6 FIXES */
/* ------------------ */
img {border:none;display:block;}
/*display block to avoid IE6 whitespace on inline elements
due to baseline spacing (for descender space),i.e. images*/ 

.inline {display:inline;}
/*used to fix IE6 double margin bugs*/  

.haslayout {height:1%;}
/*used to fix IE6 haslayout bugs*/  

.button {overflow:visible;display:block;}
/*add this class to form buttons with issues*/

a, a:link, a:visited, a:hover, a:active {color:red;}
/*link styles should be in the order LVHA esp for IE6 to display them well*/

Also, avoid/beware overuse of widths, heights, margins (esp with floats), too many position: relative’s (esp. nested position:relatives), widths + heights + padding + margin (box model issues, add padding/margin to fixed-width child elements). There are many more issues and many other ways to solve them, but generally most can be solved via fairly well documented locations, a good one here, otherwise search on google.