One page layouts
This is something that I always take for granted, but given the amount of clients that seem to have a problem with this I thought that I should point it out.
And this impresses me because it should apply to many parts of your efforts. If you can go for a single page website it is a yes from me.
But even if you have a store. Make sure that you have a one-page checkout widget installed.
According to LEMONSTAND, a one-page checkout might even give you a 21.8% conversion boost.