The Diggle Nog! achievement states:
Diggle Nog! - Make some Diggle Nog. Who doesn't love a nice cold glass of Diggle Nog?
Since I've never played this game, I have no idea what to do to get it. What is the fastest/easiest way of doing it?
This took me about 20 minutes of play to achieve (although I've played the game plenty before, so know how it all works), so it should be fairly straight forward to achieve even if you're new to the game.
Therefore, to get the achievement you need to find all three craft items and a Porta-Still to combine them with. Craft them together and that's your achievement.
So, to minimize the time to get this achievement I'd highly recommend starting with the Alchemy skill so that you start with some Aqua Vitae (which will probably be in your quick bar, not your inventory) and a Porta-Still. You'll then need to find the other two items yourself, but they're fairly common items that you should be able to find somewhere on the first level.
Keep on the lookout for Drink Machines:
If you take Burglary as a skill, you can steal random liquor from drink machines, which may speed up your acquisition of the Grog. Otherwise, check each one you find to see if they're selling any.
Diggle Eggs are found frequently in Diggle Nests, which are small rooms containing a couple of Diggles and usually nests filled with eggs: