As others say, prepare, enjoy, but don't hang around.
It is some years since I've done that trip, but it's worth remembering that you can go too fast. On a couple of occasions, especially when coming up from the Isle of Dogs, I arrived below Richmond Footbridge/Lock before the tide was high enough for the for the half-tide sluice gates to be lifted. It's a good excuse to use the lock to add to the logbook; don't know if they still charge for using it though.
On another occasion I just stooged around until the gate was lifted; found out that it does drip a lot at first!