1) To properly fix items to plasterboard walls, you need to use specialized fixings rather than ordinary wall plugs, as plasterboard is too soft for wall plugs to grip securely.
2) The strongest fixing is the Redidrive, which involves drilling a small pilot hole and screwing a plastic anchor into the hole to provide an anchoring point for screws.
3) Other effective fixings include plastic toggles, hollow wall anchors, spring toggles, and hammer-in anchors, which all work by expanding behind the plasterboard for a secure grip. Heavier items are best fixed with Redidrives or attached to wall studs.