Although ths was an old post I am sure many people with find this video very useful as it explains the basics of pruning out your tomato shoots.
As my video skills are nothing to write home about, I think that this video from Fine Gardening featuring Lee Reich, make an excellent job of explaining how to prune your indeterminate tomato plants.
The only difference is that I grow mine in the poly-tunnel, supported on crop wires, as opposed to on canes outside. However, the rules are still the same. I think Lee has left some shoots get quite long just to give a better view of the shoots, but it is best to nip them out as early as possible.