1. The system used in this tutorial has the following installed : Tomcat 6.0.14, Apache 2.2.8
  2. See on <tomcat_home>/conf/server.xml
    <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" />
  3. Download mod_jk from here
  4. Install mod_jk in Apache module directory
    • On Linux, usual location : 
      • /usr/lib/apache/
      • /usr/lib/apache2/
      • /usr/local/apache/libexec/
    • On Windows, usual location :
      • C:\Program Files\Apache Group\Apache\modules\
      • C:\Program Files\Apache Group\Apache2\modules\

  5. Here is the minimum which should be set in httpd.conf directly or included from another file: 
    # Load mod_jk module
# Update this path to match your modules location
LoadModule jk_module libexec/mod_jk.so
# Declare the module for
# AddModule mod_jk.c
# Where to find workers.properties
# Update this path to match your conf directory location (put workers.properties next to httpd.conf)
JkWorkersFile /etc/httpd/conf/workers.properties
# Where to put jk logs
# Update this path to match your logs directory location (put mod_jk.log next to access_log)
JkLogFile /var/log/httpd/mod_jk.log
# Set the jk log level [debug/error/info]
JkLogLevel info
# Select the log format
JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "
# JkOptions indicate to send SSL KEY SIZE,
JkOptions +ForwardKeySize +ForwardURICompat -ForwardDirectories
# JkRequestLogFormat set the request format
JkRequestLogFormat "%w %V %T"
# Send everything for context /examples to worker named worker1 (ajp13)
JkMount /examples/* worker1

    A complete documentation of Apache configuration is available in Apache HowTo.

  6. Here is a minimum workers.properties , using just ajp13 to connect your Apache webserver to the Tomcat engine, complete documentation is available in Workers HowTo. 
    # Define 1 real worker using ajp13
worker.list=worker1 

# Set properties for worker1 (ajp13)
worker.worker1.type=ajp13
worker.worker1.host=localhost
worker.worker1.port=8009
worker.worker1.lbfactor=50
worker.worker1.cachesize=10
worker.worker1.cache_timeout=600
worker.worker1.socket_keepalive=1
worker.worker1.socket_timeout=300

    You can compare the properties for worker1 with Connector port on <tomcat_home>/conf/server.xml

[Source]