Battle Moveset

A Good Moveset for Ludicolo would have to be this:

Attacks:

Rain Dance
Dive
Toxic
Leech Seed

Items Attached:

Leftovers

Preferred Nature:

Bold

Strategy Using Ludicolo

Ludicolo is quite the unique pokemon, its ability, Rain dish works well with Rain dance. It has good special defense but below average defense.
This moveset is basically sapping your opponent's energy while doing more damage with toxic. Set up a Rain dance to begin the Rain dish effect. Leech seed afterwards for you to drain your opponent's energy.
With leftovers, your HP is also recovered too, so if you do take damage, its entirely probable that you can recover some of the health back.
Toxic and dive work well together too, toxicing your opponent will also deal that extra bit of damage at the end of the turn. Dive allows you some time for toxic to do more damage.
The nature, Bold, boosts defense, which it needs and lowers its attack strength, which isn't used. Also, EV's to boost HP and its defenses are always a good idea when you plan to stay in the battle for a long time.
So, a simple moveset that is easy to use, can't go wrong with a few differences in the moveset too.

EV Corner:

Max out the EVs in HP for Ludicolo with any remaining in Defense & Special Defense

Strategy Against Ludicolo

Ludicolo's Defense is lower than it's Special Defense so a pummel of Physical attacks should work nicely

Contest Moveset

A good Contest Moveset for Ludicolo would have to be this for the Beauty Contest best with Modest, Mild, Rash or Quiet Nature:

Attacks:

Rain Dance
Hail
Surf
Ice Beam

Items Attached:

Blue Scarf

Strategy Using Ludicolo

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

Locations in Games

Ruby/Sapphire Evolve Lombre Colosseum Trade from R/S Fire Red/Leaf Green Trade from R/S

Animé Appearences

Ludicolo has had a couple of Anime Appearences. First, it appeared in the new TR base in Hoenn whenever the Pokémon were dancing. After that, it was owned by a Mexican trainer who battled Ash with it Short 6: Gotta Dance! Episode 343: Dancing Battle! Ludicolo!