"I have just taken up a new hobby, sketching and painting. I love painting with acrylic paints, but I find they dry up very quickly on my palette, and, what's more, it is impossible to get the dried up paint off the palette, is there a way of stopping this?"
You should find that acrylic paints are water-soluble and a few drops will do the trick as long as the paint hasn't already dried.
You can also buy disposable card palettes from art shops which may help.
You can buy a retarder from art shops (in a tube usually next to the acrylic paints). You mix this in with the paint and it slows the drying right down. Or try using PVA glue, which makes the paint last longer.
You can also get a pad of paper palettes that you put over your hard palette, and you can throw them away afterwards. Or cover it in clingfilm or greaseproof paper.