Moves
Toxic Spikes is Nidoqueen's niche, as it is one of the most consistent and bulky users of the move in OU, so it's a mandatory moveslot. Although it can use Stealth Rock instead of Protect, Nidoqueen prefers the latter to take advantage of potential sand, receive additional Black Sludge recovery to make up for its lack of a recovery move of its own outside of Rest, and scout Choice item users like Flygon and Jirachi. Protect can also be used in conjunction with Toxic Spikes to wear down opposing Pokemon with residual poison damage. However, often teams that use Nidoqueen will want it to use both entry hazards, so using Stealth Rock over Protect will be mandatory if nothing else on the team can better use Stealth Rock.
Earthquake is Nidoqueen's strongest STAB move, hitting Pokemon like Tyranitar, Heatran, and even Jirachi quite hard. Earth Power is an option over Earthquake to hit Metagross harder that also allows Nidoqueen to use a Bold nature instead, but if using Earth Power, Nidoqueen should use Flamethrower or Thunderbolt to take advantage of being faster than most Skarmory. Nidoqueen can also use Roar over a Ground-type move on a set that has Toxic Spikes, Ice Beam, and Protect, but this is only recommended on full stall builds.
The fourth move is quite flexible, but Ice Beam is the most recommended to give Nidoqueen leverage against Pokemon like Gliscor, Dragonite, Flygon, and Breloom all at once. Flamethrower is a solid option for Skarmory, Forretress, and Scizor, particularly the Swords Dance variant of the latter. Fire Blast could be used for its increased power, but this will likely be more unreliable versus Skarmory and Scizor because of its low PP and chance to miss; the extra damage output is typically not worth it because Fire Blast can likely still be stalled out with Roost from specially defensive Skarmory. Furthermore, since Flamethrower has more PP, Nidoqueen overall will have a higher chance to inflict a burn or get a critical hit. Thunderbolt can be used if a team has trouble with Gyarados and does not want to give it any initiative, but this move will not OHKO it unless it takes damage from Stealth Rock and two turns of sand or one turn of Life Orb damage; Thunderbolt hits Skarmory as well. The issue with Thunderbolt, however, is that ultimately it is inferior to Ice Beam or Flamethrower because it makes Nidoqueen unable to check Breloom.
Set Details
HP and Defense are maximized so Nidoqueen can take physical attacks from the likes of Dragonite, Tyranitar, Infernape, and Lucario as well as possible. Black Sludge is used to give Nidoqueen passive recovery and can be nice for punishing Trick users like Jirachi, Latias, and Rotom-A. A Relaxed nature is recommended because Nidoqueen is typically a mixed attacker.
Nidoqueen can opt for a Bold nature if using Earth Power, which allows it to outspeed most Skarmory. However, this is only recommended if opting for Flamethrower or Thunderbolt to damage Skarmory. While Nidoqueen is not a good Skarmory check even with these moves, as they likely will do less than 50% to it, they do prevent it from being able to freely set up on Nidoqueen with little to no consequence, which is the case if opting for Ice Beam.
Usage Tips
You need to be somewhat careful when using Nidoqueen because one of its biggest weaknesses is that it can be chipped down easily, so try to use its Poison / Ground typing to your advantage by pivoting it into attacks or status moves it's immune to. Also, identifying Pokemon with Choice items will make it easier to get Nidoqueen on the battlefield, as its many resistances can help it take advantage of bad locks. When considering which entry hazard to use first, usually Stealth Rock is the most important one, as no matter what comes in, something will take damage. Identify the type of team you are facing before laying down two layers of Toxic Spikes, as more offensive teams will actually be crippled more by only one layer. This is because they need to stay in for a few turns to take more damage from two layers of Toxic Spikes than just one. If you know that your opponent is using Starmie, you can try to bait it out and double switch to a counter; this is especially effective if you use a Pursuit trapper like Tyranitar or Weavile. Try to take advantage of Nidoqueen's Poison Point by sending it in on Pokemon that spam U-turn and other physical attacks, provided that it will take minimal damage in the process. For example, because Nidoqueen can threaten Breloom with Ice Beam, you can force Breloom to use Spore, which ideally Breloom wants to delay for as long as possible. Even while Nidoqueen is asleep, you can still pivot it into U-turn users to threaten Pokemon with Poison Point, switch it into Trick and give away a Black Sludge, and also clear Toxic Spikes from your side of the field. If you opt for a rarer move like Flamethrower or Thunderbolt, try your best to keep it concealed until necessary to reveal it so you may surprise your opponent. If you are using a Pokemon with Wish support alongside Nidoqueen or you opt for Protect over Stealth Rock, you can afford to be a bit more lenient with conserving its health, which can be incredibly rewarding because it can result in more pressure with entry hazards and certain offenses having a harder time breaking it.
Team Options
Nidoqueen appreciates teammates that can handle Water-types, Skarmory, and strong special attackers well. Ghost-type Pokemon like Gengar and Rotom-A are naturally a great fit with Nidoqueen, as they function as secondary Fighting-type checks and spinblockers for all of Nidoqueen's entry hazards. Rotom-A is better versus Starmie than Gengar, but the Choice Scarf variants of each can outspeed Starmie and OHKO it with their STAB moves. Choice Scarf Rotom-A is a great countermeasure to Dragon Dance Gyarados, which also benefits Nidoqueen. Tyranitar can do well versus Water-types and strong special attackers with its incredible special bulk and Passho Berry, and it can consistently trap Starmie, which assists with Nidoqueen's entry hazards. Tyranitar's Sand Stream also assists Nidoqueen with wearing down its foes and restoring its passive recovery in case it faces a hail-inducing Pokemon like Abomasnow. Weavile is also a wonderful partner for Nidoqueen on more offensive builds, as the two have good type synergy. Nidoqueen also removes opposing Toxic Spikes from the field on entry, and Weavile can trap Starmie with Pursuit, forcing it into a mind game by also packing Night Slash. Magnezone can trap Skarmory and other troubling Steel-types like Bronzong and Choice Scarf Jirachi while doing decently versus Water-types, but this compounds a a Ground-type weakness, and a backup plan should be in store for Shed Shell Skarmory.
Since Nidoqueen does amazingly versus Breloom, which can often be the bane of a stall build's existence, Skarmory and Latias fit well to stop Breloom after Nidoqueen forces it to use Spore. Skarmory itself has great type synergy with Nidoqueen and can assist in setting up entry hazards as well as soft check threats like Dragon Dance Gyarados and Flygon. Bulkier variants of Latias can soft check Gyarados. Nidoqueen and Latias form a strong core of Fighting-resistant Pokemon. Latias can also switch into Ground-, Water-, and Psychic-type attacks aimed at Nidoqueen. A Calm Mind + Roar set can be used in conjunction with Toxic Spikes to spread poison.
Blissey and Clefable are great special walls that have good type synergy with Nidoqueen and can also handle all the special attacking Water-types. Milotic can also handle most Water-types, has great special bulk, and does particularly well versus Gyarados, which Nidoqueen detests. On top of that, Nidoqueen clears Toxic Spikes for Milotic, which can be a nuisance. Many other bulky Water-types like Vaporeon, some Kingdra, and Swampert pair well with Nidoqueen because they appreciate the removal of Toxic Spikes. In fact, the CroCune variant of Suicune both appreciates Nidoqueen removing Toxic Spikes and setting up its own against the opposing team. Blissey, Clefable, Latias, and Jirachi with Wish can also support Nidoqueen well. Specially defensive Empoleon makes for a good teammate that can use Stealth Rock and allow Nidoqueen to use Protect, but you should beware of the compounded Ground-type weakness.
Pokemon that appreciate Toxic Spikes support are also great teammates for Nidoqueen. Protect users like Torment Heatran, Calm Mind Raikou, and Leech Seed Shaymin can take advantage of Toxic Spikes. Heatran can do well versus Steel-types that give Nidoqueen some trouble, and Shaymin can do well versus Water-types. Celebi is another Grass-type that defensively synergizes well with Nidoqueen and can do decently versus Choice Band Gyarados and other Water-types; however, while Celebi brushes off Water- and Ground-type attacks aimed at Nidoqueen, and Nidoqueen takes Bug-type attacks like U-turn aimed at Celebi, they are both weak to Ice, so this should be considered when pairing the two together. Zapdos can add to a stall build and use a set like Substitute + Roost or even a Protect set to take advantage of Nidoqueen's Toxic Spikes.