1: Where the plans say. If it's a fairly conventional stunt-ish plane, about 15 to 20% of the wing chord back from the LE to start, then move it around until the thing files right.
2: About 1" behind the CG to start, then move around until it flies right.
3: Half the weight of your lines, to start, then change until it flies right.
4: Sparky has a series of videos he's working on, but I can't find a link (Sparky, if you see this, the first place I went to was stunthanger.com, no "/sms" -- no luck, either.)
And, you can always ask about whatever you're specifically working on. You'll get enough advice that you'll be able to pick and choose which to follow.