The Serpentshrine Cavern is one of two new raids joining World of Warcraft: The Burning Crusade Classic in the second content phase of the game. But to enter the Serpentshrine Cavern and obtain all the precious treasures in it, you must first be attuned with this instance. 

In the traditional way of attunement, you must complete a long chain of tasks, which includes a trek through outland to obtain the key that allows you to enter the cave of the Serpentshrine Cavern. Here is how to attune the Serpentshrine Cavern in  World of Warcraft: TBC Classic. 

The Slave Pen
To begin the tuning process, start the Slave Pens dungeon on heroic difficulty. You must be level 70 to start the coordination chain, so make sure you have upgraded before entering the Slave Pens. If you want to reach level 70 quickly, you can buy Cheap Classic TBC Gold in the MMOSO store. 

After entering the instance, clear the dungeon all the way until Mennu the first boss betrayer. 
After clearing the first boss, you will find an NPC named Skar'this the Heretic. He will give you a task called "The Cudgel of Kar'Desh", which requires you to find two signets in Outland. One of them is relatively easy to obtain, while the other should be available with more effort. 

Get the first signet
After accepting the Skar'this' quest, the first stamp you should try to track is the Blazing Signet in Karazhan. This part of the tuning process is by far the longest, but getting rid of it early will make the rest of the journey relatively simple. 

The first step to receive the Blazing Signet is to use the Violet Eye to reach the position of Honored. Violet Eye's reputation can be gained over time by killing enemies and bosses in Karazhan raids. Remember, to enter Karazhan, you must adapt to the raid. 

After obtaining the Violet Eye, took over the quest "Medivh's Journal" from Archmage Alturus outside Karazhan. This mission will start a linear chain, and eventually lead you through different areas, into several dungeons and raids in Outland and Azeroth. 

At the halfway of the linear mission chain, the mission "Kalynna's Request" will take you to Sethekk Hall and the Shattered Hall. Complete two dungeons and loot the necessary items from the final boss. 

Return to Kalynna and accept the final mission "Nightbane" required by the chain. Go to Karazhan raid, summon Nightbane, and plunder the Blazing Signet from the dragon's corpse. 

Looking for the second signet
The second signet is easier to obtain because you only need to complete Gruul's Lair Raid to find it. 
Go to Gruul's Lair in Blade's Edge Mountains with your raid team, defeat Gruul, the final leader of the instance, and plunder the Earthen Signet from his corpse. 

Back to the slave Pens
Holding the Blazing Signet from Karazhan and the Earthen Signet from Gruul's Lair, the Skar'this the Heretic returned to the Slave Pens on Heroic difficulty.

Turn in the original task "The Cudgel of Kar'Desh" he gave you to get your reward: attunement to Serpentshrine Cavern. 

The above is about attune the Serpentshrine Cavern's detailed process. Players who have time can try it out. Buy Classic TBC Gold For Sale will make it easier for you to complete the task.