Andariel has several special qualities that make her worthy of farming. She has the highest drop rate for many of the most commonly used Uniques and Sets, the highest drop rate for rings (You can find Stone of Jordan or a Bul Kathos’s ring three times as frequently as at Mephisto), and also has by far the highest chance to drop charms. Other than a high chance to drop valuable unique, set and magic items, Andy also has the highest chance to drop High-runes up to Lo.
Andariel mainly deals poison damage and is surrounded by a bunch of monsters, so you should have good defense against physical damage and poison damage as well. Survivability against physical damage can be boosted by increasing your block chance, your physical damage resistance (capped at 50%), your faster hit recovery, your faster block rate, or having a high amount of life. Against poison damage you can use Antidote potions, and as for gearing options, your best choices are Venom Grip gloves, Guardian Angel body armor, Andariel’s Visage helm or Sandstorm Trek boots.
She can be found fairly easily, you just need to enter the waypoint to Catacombs Level 2, teleport clockwise or counter-clockwise to find the entrance to level 3, and then do the same to find the entrance to level 4. Teleporting is necessary for efficient farming, since with teleport you can move several times faster than by any other means of movement, and you can also get past walls or gaps in the map quickly. If you don’t play a sorc, use an Ondal’s Wisdom staff or a magic amulet for teleport charges.
As teleporting is such a crucial part of farming efficiency, my suggestion is to have a sorceress build for the purpose of farming Andy. The best candidate is the Lightning Sorceress, as it’s the only build capable of 7-frame teleport speed at 200% faster cast rate, allowing you to get to your targeted Boss ultra-quickly. Even with such a fast teleport speed, most of a run will consist of finding Andariel. The kill itself will take no longer than a few seconds, you should just cast a few Static Fields to lower her life by half, and cast a few Lightnings to eliminate her.
Another Pro for using a Lightning Sorc build is that it can have very high magic find % while not having to compromise on farming efficiency. Even if your inventory is full of MF charms, you can still be equipped in magic finding gear and get rid of bosses quickly.
Conclusion: Farming Andariel is one of the most profitable things you can do in the entire game, especially at the start of a ladder season. It is also the best way to gear your own character by self-found items. Use a sorceress build, optimally a lightning sorceress, and get rich super quickly early on in the season