When joining a ring to a picot of a previous ring, Teeny Tatmouse suggests trying
a down join.
Before you try this in your work, wind some thick thread, e.g. size 5 or 10 onto
a shuttle and tat a few rings - some connecting with up joins and some with down
joins. Treat all these joins as if they were the first half of a double stitch then
work the second half before continuing with complete double stitches.
Teeny Tatmouse is sure you'll agree that it isn't just a matter of preference as
to which way you direct the join - if you've worked the down join correctly, it
appears much neater.
There are, of course, exceptions. Try figuring out where an up join looks better.