I have to take a electromyography (emg) test. How do I prepare?

Relax. First you need to show up. Be prepared to sit relatively still for about an hour. The test works best if you relax during it. It is very well tolerated but there may be aspects that are uncomfortable for a very short time. The EMG portion is done with a needle that measures muscle activity. It should not be very painful. Most folks tolerate it well.The results are very useful for your treatment.
Inform your doc. Make certain to inform your physician of any blood thinners you take, and if you have a pacemaker, defibrillator, or other implantable device. (most physicians still do the EMG & the accompanying nerve conduction studies anyway, but they need to know.) take your medications as usual (unless you're told otherwise), eat something, & avoid lotions/creams or jewelry on hands/feet, if possible.