The shoots that need removing are the ones that grow from each leaf axil, not the growing shoot. This is only stopped when the plant has about 6 trusses on it in a greenhouse, less outside.

Just do a google search for images. That will show you the side shoots to go.

Have a look at this on you tube

http://www.youtube.com/watch?v=EtFnORJBQ90

Look at the pictures near the bottom of this page,under tips; http://www.thegardenersalmanac.co.uk/Data/Tomato/Tomato.htm

Someone on here once said they'd taught their children to consider the side shoots as growing in 'armpits' rather than as a continuation of the main stem. Looked at that way it might be easier to identify and remove them. :o)

If you take the side shoots off and pot them on you will get new plants or so I'm led to believe.
Should you remove the growing tip by accident leave a side shoot on and it will take over. They still produce flowers and fruit.