ESD wrist straps and mats are used to bleed off static charges and bring all items to a common level. Large current spikes will puncture and damage static sensitive electronic components. The usual method to safely reduce the static charge and limit the discharge current spike will usually use a wrist strap with a cord containing an in-line resistance between 1 – 10 Meg Ohms attached to the common ground point.
A useful online video about ESD can be found on youtube: How to Avoid ESD Damage (Official Dell Tech Support) this should give you a good practical down to earth information that your looking for and help avoid some of the more serious pitfalls. For a little more in depth explanation you might try watching: Funny video on ESD by Apple.
Some ESD wrist straps are all metal (like a watch band), and some will use an elastic band with built in metal contact points or similar conductive materials. Note: The wrist strap should be supplied with a has an embedded 1Mohm resistor in the lead (usually potted into the cable near the banana plug end).
WARNING: You must Not wear an ESD strap if attempting to troubleshoot an energized circuit with maximum voltage over 500VDC.
As always, take off rings and watches to minimize risks.
Good online sources for wrist straps would be places like Digikey, Newark, Mouser etc. Here is and example of a low cost one that Digikey can supply.
Hope this helps…