You will need a reversing starter.  With a three-phase motor, if you switch any two of the three phases, the motor will turn in the opposite direction.

The reversing starter contains two separate contactors.  One for forward and one for reverse.  Your 120V pilot control circuit will energize the appropriate starter, depending on the desired direction.  

So your control circuit will basically be "Forward" - "Reverse" - "Stop".

If this is a large motor, you may want to include a time delay to prevent switching between forward and reverse too rapidly.  

dpc

Reversing any two power leads to the motor will reverse rotation. You will need two contactors; one for FWD and one for REV.  Connect the top of the FWD contactor to L1, L2 and L3 in that order.  Wire jumpers from the top of the FWD contactor to the top of the REV contactor but swap L1 and L3 so that the REV contactor receives the power as L3, L2 and L1.  At the bottom of the contactors jumper out L1 to L1, L2 to L2 and L3 to L3 on the two contactors.  Connect the three phase motor leads to the bottom L1, L2 and L3 of either contactor.  

Your control circuit will then have to be wired STOP, FWD and REV and connected accordingly.  Run one of the 120 volt control wires (call it #1) to the STOP switch.  Then split off into two circuits on the other side of the STOP switch.  The first split goes through the FWD pushbutton, through the Normally Closed auxillary REV contacts,to the FWD coil. The other side of the FWD coil is connected through the overload contact(s) to the other control wire (call it #2). You should now have FWD working.

The second split from the STOP switch goes through the REV pushbutton, through the Normally Closed auxillary FWD contacts,to the REV coil. The other side of the REV coil is connected to the same side of the overload contact(s) that the FWD coil is connected to. The other side of the overload contact(s) should already be connected to the control circuit (#2).  You should now have REV working.

This setup will provide an electrical interlock to help keep both contactors from being energized at the same time.

A mechanical interlock between the forward and reverse contactors is highly recommended.

Hope this helps.  Good luck and be careful.

Hey thank you very much and yes this was very helpful . one more question please how do i vote for something that helped me?

Thanx DPC was very helpful.

Yes this is for DPC and langford thank you so much both responces was very helpful I am very knew here on this site and learning the ropes. I have one more question, I have been to barnes and noble  books a million and I cant find nothing that has diagrams on fwd rev and so on I have an ugly book but it is limited to its wireing diagrams  question is ....... is there a site on the net that you can get something like this from ?

Look for

"Switching, Protection and Distribution in Low Voltage Networks", ISBN 3-89578-000-6, Erlangen, München, Publicis-MCD-Verlag

A book written by Siemens employees and focusing on Siemens products, but with very good general information on the topics dicussed in this post.

Try the site below.

Look under the 'books' tab and find the 'AC Controls Handbook'. Click on it to see it that is what you want.  For $9.95 USD it's a great buy. (I am not affiliated in any way with the company).

http://www.barks.com/ElectricalApparatusDesc.asp

Consider buying an A-B 506-FJC-A2D-28R, and a leaflet will probably be found in the bottom of the box.  Rockwell Automation now features a handy online store, too.  

Also pay attention to the application.  Depending on the horsepower and torque you may need a soft start or variable frequency drive with the appropriate (constant or variable) torque rating.

kjs

Cutler-Hammer has a good site. Called cutler-hammer university on their web site.