First, warm the engine up (drive it around) for a few minutes.
Disconnect the 12V(+) lead from the coil.  Next
remove any one of the spark plugs (I suggest going in Firing order,
1,3,4,2) and insert the hose and gauge. 

Then have someone crank the engine for about 10 seconds watch the gauge,
some gauges have a tattle-tail hand to indicate the highest reading, if
yours doesn't just average what you're viewing.

Proceed through the rest of the cylinders.

Consult your Bentley Manual for readings, all values should be within
15-20% of each other.

Regards 

----------
> From: Street Bugs <strtbug@ibm.net>
> To: Multiple recipients of list <vanagon@lenti.med.umn.edu>
> Subject: how to perform a leak down???
> Date: Wednesday, December 11, 1996 3:03 AM
> 
> hi all 
> 
> got another question. can i perform a leak down test? i was checking out
my
> compression tester this past weekend and notice that it disconnects from
the
> gauge and leaves me with a hose with a fitting at each end one screws
into
> the spark plug hole and the other has a male air fitting that i could
hook
> my air compressor to. is this enough stuff to do one?  what would the
> pressure be regulated to in p.s.i.? i understand that the cylinder must
be
> at top dead and that i check to see where the air is escaping to. but are
> there any precautions or problems that i should be aware of to perform
such
> a task? must the motor be run for the day and then checked or on a cold
> motor? sorry if i ask alot of questions. i just like to have all the
answers
> before i run into more questions. thanks Jonce 
> 56 single cab 
> 66 bug 
> 66 squareback 
> 86 vanagon
> 92 jetta 
> 94 probe (wifes car)