On my back, with pillows propped up behind me. Sometimes I put a hard pillow under my bum for deeper penetration. Having a towel underneath your pelvis is handy too, for those little outbursts when squirting/cumming!!
on my front - usually in bed lying down head comfortably on a pillow or inbetween two pillows and imagining all sorts of filthy thoughts and no toys used just bad thoughts. If watching porn, then i masturbate sat in a chair.