As has been noted above, if you're learning, some of the things above will become more relevant later in the journey.
Get a biggish board. You're better to be 10 litres too big than 10 litres too small when learning. It will make your time above water easier and you'll learn faster. After a year, you might think of downsizing to the right board.
Biggest thing for me was gybing. Always switched my feet when dead downwind on windsurf board. Big no-no on foil. Could not break the habit. So learned how to ride toeside first, then went into gybes toeside exiting heelside without feeling like my feet were wrongly placed. Toeside is hard to learn, so find smooth water so that the chop interferes less with foil control. Narrow your stance before doing the foot swap. Wide stance tends to mean when back foot goes to the front, the board tends to dive harder and it's more difficult to keep it from touching down.
Also, don't think about footstraps. While getting your basic skills down pat, you often need to shuffle your feet around and I found they just get in the way. Clean board to begin. When you advance, then think about where they need to be. If you are struggling with foot placement and use the footstraps as location markers, then put something on your board (electrical tape, non permanent marker) to located your feet.
Good luck with the journey. It's fantastic and challenging.
