obi
formerly david stone
+7 Focus Punch (charge message)
+6 Switching / Fleeing
+5 Helping Hand
+4 Magic Coat, Snatch
+3 Detect, Endure, Follow Me, Protect
+2 Feint
+1 Aqua Jet, Bide, Bullet Punch, Extremespeed, Fake Out, Ice Shard, Mach Punch, Quick Attack, Shadow Sneak, Sucker Punch, Vacuum Wave
±0 Assist, Me First, Metronome, Mirror Move, Sleep Talk, Everything else
-1 Vital Throw
-2 Focus Punch
-3 Avalanche, Revenge
-4 Counter, Mirror Coat
-5 Roar, Whirlwind
-6 Trick Room
A faster Pokemon always goes first within the speed bracket of the move. In every single case, higher priority moves go before lower priority moves (if the move is selected by Assist, Me First, Metronome, Mirror Move, or Sleep Talk, that counts as a use of Assist / Me First / Metronome / Mirror Move / Sleep Talk, and thus it has a priority of 0)
Quick Claw gives your Pokemon an 18.75% chance of ignoring Speed and going first within your speed bracket, barring the enemy also activating a Quick Claw, in which case normal Speed rules would apply. Speed and Quick Claw never let a move with a lower priority beat a higher priority (so a Quick Claw activated Deoxys-E using Vital Throw always goes after Macho Brace Paralyzed Shuckle using Tackle). Custap Berry makes your next move automatically go to the top of its priority bracket after activating.
The exceptions are Assist, Me First, Metronome, Mirror Move, and Sleep Talk. These have a priority of 0, and thus if you Sleep Talk Whirlwind, for example, you can go before a slower Pokemon using, say, Tackle.
Unlike in GSC, it is the faster phazer that phazes. In GSC, a Pokemon had to go last for phazing to work, so if a Tyranitar with 1 Curse and a Tyranitar with no Curses both used Roar, the non-Cursed Tyranitar would go first, and Roar would fail, and then the Cursed Tyranitar would go, and phaze out the other Tyranitar. In Advance and DP, however, the faster phazer uses Roar / Whirlwind, sending the enemy away, thus giving them no chance to try and Roar / Whirlwind you.
Revenge and Avalanche get boosted damage from Focus Punch, and do not interrupt it, making them the only attacks that cannot interrupt Focus Punch.
Lagging Tail, Full Incense, and Stall make that Pokemon always move last, if both Pokemon are using a move of the same priority. Lower priority moves will still always go after higher priority moves, regardless of Lagging Tail, Stall, and Full Incense. If two Pokemon with Stall are out at the same time, the one with higher Speed goes last. If two Pokemon are holding Lagging Tail or Full Incense at the same time, the one with the higher Speed goes last. If a Pokemon with Lagging Tail / Full Incense is out against a Pokemon with Stall, the one with Lagging Tail / Full Incense goes last. If a Pokemon with Stall activates Quick Claw, the that Pokemon will still go first, barring a faster Quick Claw activation.
Trick Room reverses the use order of the moves in the same priority. For instance, if a Pokemon with 3 Speed is up against a Pokemon with 10 Speed, the one with 10 Speed would normally go first, but under Trick Room, the one with 3 Speed goes first. +2 priority will still always beat +1 priority, however. Pokemon with Lagging Tail / Full Incense and Stall completely ignore Trick Room, so they go last in the order explained above. Pokemon with Quick Claw completely ignore Trick Room as well, so Quick Claw still makes you go first, and if two Pokemon activate their Quick Claw, the faster Pokemon still goes first.
Pursuit comes right before a switch if a switch is used (+6.5 priority, if you want to think of it that way). It doubles in power if they switch out. If they use Baton Pass and you are faster, the Pokemon using Baton Pass takes normal damage. If they use Baton Pass and you are slower, the Pokemon they pass to takes normal damage. If they use U-Turn and you would normally go before them, the Pokemon using U-Turn takes normal damage. If they use U-Turn and you would normally go after them, the Pokemon using U-Turn takes double damage, and then they select the Pokemon to bring out, which takes no damage, so essentially, if you use Pursuit and they use U-Turn and you would normally go after them, Pursuit has 0.5 priority (so in Trick Room, you would have to be faster than them to get the boost, unless their Quick Claw activates or you are holding Lagging Tail / Full Incense or have the trait Stall).
+6 Switching / Fleeing
+5 Helping Hand
+4 Magic Coat, Snatch
+3 Detect, Endure, Follow Me, Protect
+2 Feint
+1 Aqua Jet, Bide, Bullet Punch, Extremespeed, Fake Out, Ice Shard, Mach Punch, Quick Attack, Shadow Sneak, Sucker Punch, Vacuum Wave
±0 Assist, Me First, Metronome, Mirror Move, Sleep Talk, Everything else
-1 Vital Throw
-2 Focus Punch
-3 Avalanche, Revenge
-4 Counter, Mirror Coat
-5 Roar, Whirlwind
-6 Trick Room
A faster Pokemon always goes first within the speed bracket of the move. In every single case, higher priority moves go before lower priority moves (if the move is selected by Assist, Me First, Metronome, Mirror Move, or Sleep Talk, that counts as a use of Assist / Me First / Metronome / Mirror Move / Sleep Talk, and thus it has a priority of 0)
Quick Claw gives your Pokemon an 18.75% chance of ignoring Speed and going first within your speed bracket, barring the enemy also activating a Quick Claw, in which case normal Speed rules would apply. Speed and Quick Claw never let a move with a lower priority beat a higher priority (so a Quick Claw activated Deoxys-E using Vital Throw always goes after Macho Brace Paralyzed Shuckle using Tackle). Custap Berry makes your next move automatically go to the top of its priority bracket after activating.
The exceptions are Assist, Me First, Metronome, Mirror Move, and Sleep Talk. These have a priority of 0, and thus if you Sleep Talk Whirlwind, for example, you can go before a slower Pokemon using, say, Tackle.
Unlike in GSC, it is the faster phazer that phazes. In GSC, a Pokemon had to go last for phazing to work, so if a Tyranitar with 1 Curse and a Tyranitar with no Curses both used Roar, the non-Cursed Tyranitar would go first, and Roar would fail, and then the Cursed Tyranitar would go, and phaze out the other Tyranitar. In Advance and DP, however, the faster phazer uses Roar / Whirlwind, sending the enemy away, thus giving them no chance to try and Roar / Whirlwind you.
Revenge and Avalanche get boosted damage from Focus Punch, and do not interrupt it, making them the only attacks that cannot interrupt Focus Punch.
Lagging Tail, Full Incense, and Stall make that Pokemon always move last, if both Pokemon are using a move of the same priority. Lower priority moves will still always go after higher priority moves, regardless of Lagging Tail, Stall, and Full Incense. If two Pokemon with Stall are out at the same time, the one with higher Speed goes last. If two Pokemon are holding Lagging Tail or Full Incense at the same time, the one with the higher Speed goes last. If a Pokemon with Lagging Tail / Full Incense is out against a Pokemon with Stall, the one with Lagging Tail / Full Incense goes last. If a Pokemon with Stall activates Quick Claw, the that Pokemon will still go first, barring a faster Quick Claw activation.
Trick Room reverses the use order of the moves in the same priority. For instance, if a Pokemon with 3 Speed is up against a Pokemon with 10 Speed, the one with 10 Speed would normally go first, but under Trick Room, the one with 3 Speed goes first. +2 priority will still always beat +1 priority, however. Pokemon with Lagging Tail / Full Incense and Stall completely ignore Trick Room, so they go last in the order explained above. Pokemon with Quick Claw completely ignore Trick Room as well, so Quick Claw still makes you go first, and if two Pokemon activate their Quick Claw, the faster Pokemon still goes first.
Pursuit comes right before a switch if a switch is used (+6.5 priority, if you want to think of it that way). It doubles in power if they switch out. If they use Baton Pass and you are faster, the Pokemon using Baton Pass takes normal damage. If they use Baton Pass and you are slower, the Pokemon they pass to takes normal damage. If they use U-Turn and you would normally go before them, the Pokemon using U-Turn takes normal damage. If they use U-Turn and you would normally go after them, the Pokemon using U-Turn takes double damage, and then they select the Pokemon to bring out, which takes no damage, so essentially, if you use Pursuit and they use U-Turn and you would normally go after them, Pursuit has 0.5 priority (so in Trick Room, you would have to be faster than them to get the boost, unless their Quick Claw activates or you are holding Lagging Tail / Full Incense or have the trait Stall).