Double Battle Movesets

A Good Moveset for Plusle & Minun would have to be this:

Attacks:

Plusle	Minun
Helping Hand Protect Rain Dance Encore	Thunder Hidden Power Grass Attract Double Team
Items Attached:
Leftovers	Leftovers
Preferred Natures:
Timid	Timid
EV Spread:
As Much as Poss. in Speed, rest in Special Defense & Defense	As Much as Poss. in Defense, rest in Special Defense & Special Attack

Strategy Using Plusle & Minun

Minun and Plusle, both pokemon lacking in defense and can be taken out by most physical sweepers. The idea of this moveset is to support each other. Rain dance from Plusle and followed by Minun's thunder can be very effective. Also, Helping hand + HP Grass or Thunder(especially after rain dance has been used) can be very effective. But the chances of Plusle and Minun lasting in battle is slim.
Protect can help these pokemon in tough situations. Encore is basically to annoy your opponent and may force them into repeating a move that isn't an all out attack given Minun a chance to attack again.
Attract and Double team on Minun is there to add to the team strength with Attract infatuating your opponent if their pokemon's gender is opposite to your Minun. If you want to use these pokemon on their own I suggest turning them into baton passers with movesets like: Baton pass, Agility, Attract/Charm, Thunderbolt. Even as a baton passer they don't have the best moves available to them.

Single Battle Movesets

A Good Moveset for Plusle & Minun seperately would have to be this:

Plusle	Minun
Baton Pass Agility Attract Thunderbolt	Baton Pass Agility Charm Thunder Wave
Items Attached:
Leftovers	Leftovers
Preferred Natures:
Timid	Timid
EV Spread:
As Much as Poss. in Speed, rest in Special Defense & Defense	As Much as Poss. in Defense, rest in Special Defense & Special Attack
Strategy Using Plusle:	Strategy Using Minun:
Plusle on its own is best as a baton passer since it won't last long on your team, especially against physical sweepers. Just do a few agilities and baton pass to a different pokemon. Attract and thunderbolt are filler moves.	Minun is very much like Plusle and should be used as a baton passer. Just like Plusle, Agility and then baton pass to get the most out of this pokemon. Charm and Thunderwave might prove useful and stall your opponent long enough to do more agilities before baton passing.

Strategy Against Plusle & Minun

Plusle The Attacker, Minun the Defender...however both their physical stats are poor you your best bet here is to get in with an Earthquake and they'll be toast. Any Super Effective or powerful physical attack will work

Contest Moveset

The best Moveset for Plusle OR Minun would have to be this for the Cool Contest best with Lonely, Adament, Naughty or Brave Nature:

Attacks:

Rain Dance
Thunder
Thunderbolt
Thunder Wave

Items Attached:

Red Scarf

Strategy Using Plusle OR Minun

If you do the attacks in this following order you should have very few problems; 1st - Rain dance, 2nd - Thunder, 3rd - Rain dance, 4th - Thunderbolt, 5th - Thunderwave

Locations in Games

Ruby/Sapphire Route 110 (Both) Colosseum Pyrite City (Plusle only) Trade from R/S (Minun) Fire Red/Leaf Green Trade from R/S/C (Both)

Animé Appearences

Plusle & Minun have had several Animé Appearences. Firstly, they were used by Kazuchi at a Lighthouse and he wanted Ash to help him train them. After that Kazuchi was training in a tournement with them. After that they were in LaRousse City and kept causing mischief with Ash and Gonbe. After that, they help Pikachu find the Azumarill that was supposed to star in the festival Episode 314: A Different Kind Of Misty! Episode 328: Plusle & Minun! Road Assistence! Episode 353: Formiddiable Enemy! Mother Co-Ordinator Enters! (Plusle Only) Movie 7: Visitor Of The Space Fissure Short 7: Pikachu's Summer Festival