Some nice tips at the LA Times:
Moisture in the potatoes is the enemy because it means having to add more flour. So you want to start out with potatoes with lower water and higher starch content — Idaho or other russet baking potatoes work well, and Yukon Gold or other sweet, waxy varieties do not. Potatoes get starchier as they age, so older potatoes are actually preferable here.Much more, including a video and recipe at the link. I've actually only made gnocchi the one time, and Anna recently mentioned wanting to tackle the dish again, so maybe this will serve as inspiration. Giving clear directions on what you're trying to achieve (and why) is something many recipe sites and cookbooks fail to consistently do... and thus Colicchio's comments on gnocchi shows one of the main reasons I like these "Master Classes" by the LA Times... and note that it's value is completely separate from the recipe.
You want to encourage the potatoes to release as much of their moisture as possible during the cooking process. Prick the skins all over with a fork before baking them; slice them open immediately out of the oven; and — trying your best not to burn yourself — scoop the steaming hot contents of the potato into a fine ricer or food mill as soon as possible. These three things will help steam escape.
Once you've riced the potatoes and turned them out onto a clean work surface, it's time to make the dough. Working a pastry bench scraper in chopping motions, distribute the potato evenly across your work surface, then drizzle that with your beaten egg yolk. Add pepper.
The flour that we use for gnocchi is what's called doppio zero in Italy — "00 flour" to us Americans — which is very finely milled and soft as talcum powder. It leads to a smoother, more supple, malleable dough, which is why it's often used in pizza dough and fresh egg pastas.