What you can take advantage of
- They are dumb
- Up till around 20-28, they can't do anything at all from my experience
- Move Tutors. There are plenty with some good moves.
- The shop next door. Some useful items like Choice Bands.
- Smogon should help you with sets (do not take the example ones I used in my answer as they are random crap)
- Try experimenting such as different leads movesets and Pokemon. One doesn't work try another. Let's say that I don't see my Greninja working out too well. I rebreed and give it a different nature and moves.
- Use your brain. Don't be the NPC! They can't think very well but they aren't very dumb. Always think your decision through before picking a move.
- Analyze the situation. What's the best way to get through? Which move should I use? Which mons go well together on my team? Which mons should I use next?
- Never ever rely on luck. Ever. If a move like Will-O-Wisp misses or you think the opposing Ferrothorn is a stally one as the Battle Maison tends to run weird sets and EV spreads.
- Follow the above xD
Now check out Crimson's answer below. That should explain singles better as I'm not very good at battling and especially singles.
Best way to get through in singles
I read this somewhere before. Glibliss + Mega Kangaskhan.
>This is a very effective, if not the best strategy to get win streaks at the Battle Maison.
Gliscor and Blissey cover almost everything defensively, and Kangaskhan has offense covered.
Just lead off with Kangaskhan, and attempt a sweep. If something goes wrong you always have Blissey and Gliscor as a backup.
Eviolite Chansey is also an option, probably better than Blissey actually.
This works best in singles, but is usable in double and possibly also triples, although you need to add some Pokémon.
>Here are the sets:
>Gliscor @ Toxic Orb
Ability: Poison Heal
EVs: 252 HP/ 232 Def/ 20 Spe
>Blissey @ Leftovers
Ability: Natural Cure
EVs: 252 HP/ 252 SpD/ 4 Def
>Kangaskhan @ Kangaskhanite
Ability: Scrappy ---> Parental Bond
EVs: 252 Atk/ 252 Spe/ 4 HP
Directly sipped from here. All credit goes to Crimson.
Note that I am going to suggest what I do! Do not take any of these sets as they are crappy example sets!
Now as I have more experience with doubles, this might not be a tremendous help, but I'll do my best!
So first, try getting some support such as Tailwind or weather depending on what your team needs. So let's say I have a Bisharp (which I do) and I need Tailwind support. I chose Talonflame.
Talonflame @ No item
EVs: 200 Atk/180 Spd/100 Def/28 Hp
Ability: Gale Wings
That is somewhat what a support Talonflame would look like. So after that, I have Tailwind support! :D
Next the Bisharp. I want something fast and offensive.
Bisharp @ Life Orb
EVs: 200 Atk/220 Spd/88 Hp
This is what I choose and works well with the other Pokemon.
Now let's say that Talonflame dies too easily to Rock-type attacks. I need a good switch in.
Breloom @ Focus Sash
EVs: 200 Atk/200 Spd/108 Def
This serves as a rock killer as well. But too weak to flying right? And we need more coverage. So I choose an Ice-type.
Glalie @ Glalite
EVs: 220 Atk/220 Spd/68 Hp
Ability: Ice Body ---> Refrigerate
Note that none of these mons work well together!
For team-building in doubles, always remember the following!
- Stall is not as easy in doubles.
- Many strategies won't work in this as in singles.
- Setting up is much harder as they may know what you are going to do so they will target the set-up mon.
- Protect will help in many cases. Earthquake anyone? Protect will really be useful here!
I don't think this is clear, but hope I helped!
-It's a secret!