====== Lithography ====== 

Like making ICs. You start by putting on a photoresist, typically by spin coating. Next, a concentrated light (eg: laser or mask) exposes (or doesn't expose depending on the type of photoresist) the area that you want to etch. Finally, the area is chemically etched away.

Photoresists
http://cleanroom.byu.edu/photoresists.phtml

====== Laser cut ====== 

A high power pulsed laser is fired at the area to be removed. Professionals seem to lean towards this for its ease of use and repeatability.

====== Physical abrasion ====== 

A microprobe scrapes the traces away. Professional units use ultrasound to make the cutting more reliable.

====== Nail polish ====== 

Tarnovsky seems to favor using nail polish to form a mask. He then scrapes the to be removed area's mask away with a probe and chemically etches. His results indicate this works surprisingly well despite how crude it sounds vs other techniques.

====== Electronic ====== 

Some fuses are blown by sending pulses. Not practical in most cases since the area to cut could be very obscure.