I get very fed up when my mash doesn't turn out the way I want it, usually too sloppy and runny, too gluey or too grainy. I don't like anything in my mash except salt and butter (and plenty of the latter). What I've learned is to always hedge my bets by using at least two, preferably three, varieties of spud. I don't like spuds that collapse in the boiling water so I avoid King Edwards. Also, only a small amount of waxy sorts go in, things such as Charlotte or Nicola. Too much of those risks glueyness. Santé are very good if you can get them. I regard Lady Balfour to be horrid watery things so they don't get in. Most cookery books suggest insufficient boiling time. I reckon thirty minutes is the minimum. If I've put plenty of butter in but the mash is still a bit too stiff, under protest I'll add a drop of milk. I have a potato ricer but using it for mash risks the spuds cooling down too much. I've used it successfully to make gnocchi, for which I boil the spuds in their skins which I can slip off later. That stops the spuds from going too soggy, not great for gnocchi.

Another golden rule is to buy only the best spuds. Even the most expensive spuds are cheap.