related posts without a plug in

I’d like to create related posts without a plugin. I had tried Zemanta but they add backlinks to every post which I did not like. I have read a number of tutorials and think I can get the Wp query part but I can’t seem to style it in CSS. What happens is that the related posts show up in a bullet point list and the images are a mess.

Is there anyone out there that would share their code for related posts, preferably by category, or just random posts, along with the CSS for displaying it vertically with thumbnails.

Tx