Most of the points tmproff has suggested are good except:
ORIGINAL: tmproff
9. To help with wing rock, adjust both left and right ailerons up about 1/4 - 1/2 of an inch
A good 3D setup leaves your plane pretty symetrical. Reflexing the ailerons may help in a harrier but it'll also have an effect (perhaps bad) in knife-edge and other maneuvers. It's far better to learn how to control the wing-rock by changing the attitude/power to find a more stable harrier position.
10. Adding in a mix that slaves your ailerons to your up elevator (only about 10-15%) helps stabilize a hover (this causes inverted harriers to be more difficult tho)
What?
Hovering requires little more than lots of practice. It's actually one of the easier 3D maneuvers and anyone who needs the crutch of mixing just to get the hang of hovering is taking the wrong route (IMHO).
When it comes to flying 3D, mixes are for people who can't actually use their thumbs/fingers properly.
If you choose a good model then none of this mixing or reflexing will be necessary. My Mojos almost hover by themselves (I can take my hands off the sticks for up to 10 seconds or more and they'll just sit there) but they do require a little elevator in knife-edge. The Katana V2 by comparison does superb knife-edge only requiring rudder to hold the nose up but it does require more effort to stop wing-rock in a harrier.
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