Trainers
Programs called trainers allow you to boost and alter your character's abilities. Trainers should only be used if you save your Diablo II characters to a personal computer, however. Characters saved to Blizzard Online's central servers, such as battle.net, will quickly be detected and suspended if trainers have been used. A number of Diablo II trainers exist that help you enhance your strength, dexterity, skills, and spells easily. Trainers can also increase the amount of money or special items your character holds.
Difficulty Settings
Diablo II adjusts the number and strength of the enemies you face based on how many people are in your party; a single player won't battle as many bad guys as four working together. By changing the number of players the computer thinks it's facing, you can customize your gaming experience. Lowering your game's difficulty helps you move through levels more quickly. Raising it raises your character's strength quickly as well as dropping additional magical items and gold. To do this, press "Enter" to open a chat box, then type "/players x" where x is a number between 1 and 8. The higher the number, the harder the level.
Glitches
There are a few glitches in the game to take advantage of. The first provides an easy way to avoid enemies. If you find yourself surrounded by more enemies than you can face, simply hit "Escape," then save and exit the game. When you reboot, you'll find yourself in the safety of town. Likewise, if you die, immediately save and exit the game. You'll find your corpse and all your items in town when you log in next.
Secret Levels
Several Diablo games contain a secret cow level. This has become an inside joke among die-hard players. To find the cow level in Diablo II, first beat the game on a certain difficulty level. Then travel back to the Rogue Encampment while on the same difficulty. Take Wirt's Leg (a magical item you will have found on your travels) and a Tome of Town Portal into the Horadric Cube and transmute it. A portal will appear but beware; there will be hordes of cows waiting for you. Once the Cow King has been killed, you cannot return to the cow level on that difficulty and must wait until you've beaten another level. However, if you don't kill the Cow King you can return to that world again and again for gold and experience.