Dress appropriately
What you choose to wear for your talk is, of course, a delicate
subject, and I don’t want to sound like your mother.
Nevertheless, other people do form an impression of you based
in part on your appearance, and so my advice is at least to
consider what statement your clothing is making. At the very
minimum, you should avoid looking like you just dragged
yourself out of bed or staggered out of the hotel bar (even if
true). To play it safe, you’ll want to dress neatly and
appropriately.