Any special tips on cooking the potato? Tell us your secrets.
Don't peel—boil them whole. This way the potato won't absorb too much water, and it takes just about as long to boil (about 20–25 minutes) were you to have peeled them.

What's the best potato ricer? And why are potato ricers important?
Oxo's potato ricer is the best. With a potato ricer, you don't need to peel your potato. The skin will stay in the ricer while the flesh will go through the holes into your bowl, leaving you with incredibly smooth mashed potatoes. Using a potato ricer will help with not overworking your potatoes, which will become too starchy if you overwork them.

Any tips for boiling gnocchi? Should the water be salty like regular pasta water?
Yes, use salted water.

If you want to make it way ahead, can you freeze the dough? If so, what's the best strategy for making a BUNCH and freezing some/most of it?
Yes! Of course you can freeze your dough. You can freeze it whole, or you can roll out you gnocchi and lay it on parchment paper-lined baking sheets to freeze. Then, transfer to ziplock bags. Boil from frozen—they'll float when they're cooked.