Moinmoin - it depends a bit on what you want to put on it and how you construct your wooden table... I also had to realise that a 28mm three-layer beech board alone is rather wobbly. I then screwed some slats underneath so that the table wouldn't bend too much... Now it actually works.
Screws: Some are supplied. They are so-so. Good wood screws with a washer will do. You can simply forget about countersunk screws.