Also, I'd encourage folks to look at the new Arcana Knacks we did for Aldis: City of the Blue Rose. Not only are there some useful tricks there, but they provide inspiration for new "tricks" with existing arcana.
Thinking it over, I may leave how I've been using test TN/result for now because I had some interesting plans for arcane items / artifacts based on what I've read in the City of Aldis book...
I end up with something like this:
Stone of Flame +3
Arcane Power. You gain the Fire Shaping arcanum. If you are already trained in this arcanum, then you gain the Flaming Shield arcana knack.
Quicken Arcana II. You can use the Fire Shaping more swiftly, reducing the cast time from a Major action to a Minor action, but you also increase the fatigue TN by +4.Stone of Healing +3
Arcane Power. You gain the Cure arcanum. If you are already trained in this arcanum, then you can use the Cure arcanum at a range, but the arcane and fatigue test TN is increased by +1 for every 2 yards beyond melee.
Empower Arcana II. When you cast the Cure arcanum, you can increase the arcane test result by +1 (even after knowing your test result), but you also increase the fatigue TN by +2. You cannot empower the Cure arcanum more than twice at a time.
We have been using Fatigue as Joe outlined and it has given it more teeth but it also rains in Adepts a bit which I think is good.
Running: Blue Rose AGE (Cat's Cradle)
"That queer Goth chick." "You are going to have to be more specific"