From Bulbapedia, the community-driven Pokémon encyclopedia.
The Dugtrio's Pit of Doom Deck is a predominantly type deck found in the Team Rocket Strategy Guide. The deck is classified as one of the advanced decks in the book, containing more rare cards than the easy-to-build decks.
Dark Dugtrio's Pokémon Power: Sinkhole makes retreating a risky proposition for your opponent. Use Pokémon Trader and Computer Search — and Professor Oak if you have to — to get Dark Dugtrio on your Bench as soon as possible. Don't settle for just one Dark Dugtrio. Get two or three if you can. Avoid using Diglett or Dark Dugtrio as your Active Pokémon. If Diglett gets Knocked Out, that's one less chance you have to play Dark Dugtrio.
Once you have Dark Dugtrio on your Bench, use your other Pokémon to put some pressure on your opponent. Hitmonchan and Hitmonlee are perfect for this. Their attacks do quite a bit of damage. Make sure you use Gust of Wind to make your opponent's Active Pokémon his or her most vulnerable one. If your opponent is playing a Grass deck, use Charmander as your Active Pokémon. Against Psychic Pokémon, Charmander or Rhyhorn should work just fine.