Filling holes in plasterboard

Best method I've found is to get a small piece of wood (or plasterboard) - just wide enough to fit through the hole but longer than the height of it. Screw a screw into the wood a little so it grips but still has enough sticking out to grab hold of. Put some no more nails or some such adhesive on the top and bottom of the bit of wood, feed it into the hole and pull it towards you so the adhesive sticks the wood to the back of the plasterboard. This will then give you a back to the hole so that you can fill it more easily.

I'm not really sure if this is really necesary on such small holes - maybe somebody will have a better suggestion but I have used that method with quite large holes succesfully.

There are a multitude of fillers to choose from - take your pick!

Mix a tiny bit of plaster and apply it to the edges of the hole with a knife blade. Allow to dry. Repeat and close as much more as you can. Never got beyond the third application here. You just put as much plaster in the hole as you can each time, without it falling through.

Cut a piece of hardboard slightly narrower and longer than the hole, drill a hole in the middle and fix a piece of string in it. Insert the piece of board into the hole, and pull the string so the board is tight against the back of the plasterboard. Apply filler. Trim string flush when filler has set.

Excellent suggestion.

I would apply Pinkgrip to the face of the hardboard before inserting it.

You'll end up with a filled hole stronger than the surrounding plasterboard.