Next time you design a new rule or game element, calculate its Table Cost. That's a measure of the strain it places on the players around the table, in terms of time, brain stress, and suspension of disbelief. Rules with low Table Cost are less annoying to use. Rules with high Table Cost are more annoying to use, and they'd better have something else going for them, or they Get The Axe!
+0: Not easily forgotten, because it's obvious when should you should use it. ("I need healing, let me see what healing powers I have left!")
+2: Somewhat easily forgotten. Your CHARACTER could be reasonably expected to remember it. When it's not the focus of attention, you don't have to think about it. ("I can activate Fire Form to get through the lava!"
+5: Easily forgotten. The PLAYER has to remember it, because it's based on a generic or a meta-game trigger. May require something to be tracked from round to round. ("I became Bloodied, so my Animal Fury kicks in!")
+0: You don't need to bother anyone else with the details (you roll 3d6 extra damage when flanking)
+2: Requires you to specify a game term aloud ("...and I do 15 fire damage")
+5: Requires you to specify a game term aloud EVERY TURN ("...and I'm using my minor action to sustain the Flaming Sphere")
+0: Provides a vivid mental picture ("I slam into him and push him back a step")
+2: Abstract ("When I hit this guy with my mace, I give you an AC bonus")
+5: Defies imagination ("So I guess the fog is prone?")
+0: Can be handled with, at most, simple addition ("My bard song gives you +2 to your skill check")
+2: Requires one or more additional die rolls ("I've hit you with my Trip touch-attack roll, so now we make opposed Strength checks")
+5: Requires consulting the manual, no matter how many times you've done it before ("I Grapple")
+0: Self-explanatory to a new player ("You can't see anything that's not in range of a light source")
+2: Easily explained, even if arbitrary ("You can't open the door in the middle of your move action because you have to complete your move action before you do your minor action")
+5: When explaining it to a new player, you eventually have to resort to "You'll figure it out once you see it in play" ("The first diagonal move of your turn costs one square of movement. The second and every subsequent even diagonal move cost two squares, even if the diagonal movements are separated by orthagonal movements that always cost 1 each.")
Table Cost must be lower than the Awesomeness Factor, an arbitrary number from 1 to 10. If the Table Cost is 11+, the Awesomeness Factor must be TRULY EPIC.
3rd edition Dodge:
Recall cost is +5: You have to remember it, not based on a specific cue, but just as part of your action.
Speech cost is +2: You need to specify it aloud with some frequency.
Belief cost: +0. It makes sense that you'd be able to guard against a chosen target.
Time cost: +0. Just adds +1 to AC.
Learning cost: +0. Makes sense.
Tracking cost: +5. You have to keep track of which opponent is currently under your Dodge.
Total Table Cost: 12.
Now let's look at the benefit. You get a +1 AC versus a single opponent - a benefit which might change a hit to a miss once every, say, 4 encounters.
Awesomeness factor: 1.
In order to support its very high Table Cost, Dodge would have to have an extremely awesome benefit: for instance, you are TOTALLY UNHITTABLE by your Dodge opponent, or whenever your Dodge opponent rolls a natural 1 on attack roll you INSTANTLY GO UP A LEVEL, or something else crazy like that.