1) Beat together the butter, sugars, salt, baking soda, baking powder and vanilla till well combined.
2) Add the egg, beating till smooth. Scrape the sides of the bowl, and beat again till smooth.
3) Add the flour and oats, beating to combine.
4) If you're making cookies using chips, nuts, etc., beat in the orange juice, then the add-ins.
5) If you're making plain cookies, without add-ins, omit the orange juice.
6) Cover the cookie dough, and refrigerate until thoroughly chilled; at least several hours, or overnight.
7) When you're ready to bake, preheat the oven to 375°F. Lightly grease (or line with parchment) two baking sheets.
8) Drop the cookies by the traditional teaspoonful (about 2 measuring teaspoons, about a 1" ball) onto the prepared baking sheets, spacing them about 2" apart. A teaspoon cookie scoop works well here.
9) If the cookie dough has been refrigerated, bake the cookies for 13 to 14 minutes, until they're a very light golden brown, and a bit darker around the edges. For unrefrigerated dough, bake for about 11 minutes. For softer cookies, reduce the baking time by about 2 minutes.
10) Remove them from the oven, and cool right on the baking sheets.
Yield: about 5 dozen small cookies (with 2 cups add-ins).