Tow line - if you buy one get an elasticated one - it is far easier to
tow
with than the non elasticated type - also, make sure there is a small
metal
crab on the end rather than a plastic clip.

Again, a good idea for a newbie? I'd be really worried about getting
one.

Wouldn't bother personally, shoujldn't be towing on moving water anyway,
and on flat water a sling and crab do just as well, and are more generally
useful.

Well you can use the sling and crab for other things, but towing with a
sling and crab is uncomfortable and the release can be awkward. I must
admit, that I've only seen a tow line used in anger once, and it was obvious
that a quick release with an elasticated shock absorber would have been much
easier on the towing paddler. The towed paddler made no effort to paddle and
was "dead in the water" as it were, so all the strain was on the towing
paddler and a sling around one shoulder would have been a real strain.

I have tow lines because I'm a coach and we use them for training and have
them handy just in case we need them. I've never taken one on a river
though.

Ewan Scott