Hi Richard,
Usually pilots keep the nosewheel on the centerline, unless there is
reason not to. Some of the posters here brought up good reasons not to
stay on center. One thing that I don't think has been mentioned is
that sometimes ATC makes the decision for you . An example would be
when two aircraft are comeing toward eachother on the same taxiway.
The dialog often goes something like this:

"Cessna 123, Somewhere Ground Control, remain to the right side of
taxiway A , watch for the Caravan approaching you"
"Cessna 123, staying to the right."

The wording can vary quite a bit, to include moving for vehicles,
equipment, new taxi clearances, etc. I also realize, obviously, (and
as mentioned by other posters) that even if ATC isn't involved or on
the field airplanes tend to steer around one another and go off the
taxi centerline

Nice meeting you Richard. We aren't all bad mannered pilots here,
please post and hopefully you will get the answers you need. Don't let
the few turds around here keep you away- I don't post much, but there
are some really great people in this group.

Jamie