A little help with optics would go a long way...!

Hi, I'm trying to design an engraving device and am having some trouble narrowing things down...

I have chosen my diode laser (http://www.ebay.com/itm/2W-2000mW-445nm-Blue-Laser-Diode-TO-18-5-6mm-M140-/321715074421?hash=item4ae7b67575)

My question is, how should I focus this? is it normal to focus a laser with a single lense? Or do people typically use beam-expanders?

what is the best approach to achieve a small spot size? 500 microns or less? Distance of the work-plane and laser can be adjusted.