My amateurish approach: I don't bother to set lenses, as that
requrires going through the menu - I just screw TC-E2 on and take a
photo. Two things on the checklist though: (1) make sure zoom big
enough so no vignetting (2) make sure shutter priority with shutter
speed over 1/250, otherwise find some stabilization.
ad 1. In bright light it is easy to miss some small vignetting on
corners - the LCD is not that readable in sunlight.
ad 2. I never use a standard tripod, so (2) is important. However,
I do carry a mini-tripod called 'bendy legs' which is invaluable
and it can be mounted on a park bench, tree branch etc.
I did consider TC-E3 when buying but went for E2 - it was smaller
and I an SLR refugee so paranoid about that. Your opinion may
differ.
Thanks so much everyone for the very useful advice. I am going to
go for the TCE2. Plan to go to the zoo next weekend, which should
offer plenty of chances to try it out. Any further advice on how to
get the best from it regarding camera settings etc ?