example: 
inside the file i targeted i found the hashed password like this 
blah:S2XSgk2WEfE9w 
so saved to list ready to crack , i called mine MD5pass for this lesson 
this is what jtr will be cracking,
after you have several passwords to various sites you can begin jtr or just use a single hashed password ..its up to you 
now there are many ways to crack the file using jtr am just going to use the basic 
one i find the easiest but slowest to use...there are plenty of jtr guides around for more detail cracking modes
common modes are 
john -si [passfile]
john -w:[wordlist] [passfile]
john -i [passfile]
there are other modes using digits,alpha,all...they all do the same thing... anyway on to basics 
assuming you have john in C:\ directory just type
c:\john -i MD5pass.txt 
image 1

after several minutes\hours you should have something like this with cracked passwords if you take a look at the image
after 21 minutes it had cracked 13 of the 36...not bad after 3hrs 24min 18 cracked...half done  btw each password cracked is a website....so up to now 18 possible targets 
image 2

to check progress hit any key 
to stop the cracking hit Ctrl+c session aborted
to view your results type: 
c:\john -show MD5pass.txt>result2.txt....this will save the file called result2.txt in the jtr root like this 
image 3

you now have the password to gain access to the ftp,or whatever 
to resume your cracking
type: 
c:\john -restore 
will load the remaning uncracked passwords and resume attempts from were it left off 
image 4

JTR Commands and Modes 
**if you look in the doc folder that came with JTR it gives you details on how to use them** 
hope you enjoyed the tutorial...remember if you do gain access to a site\server please inform the admin 
i hold no resposibility for your actions 
ComSec
23 june 2003 
dont come any easier than this...i think !