There are several different quest to obtain some special jobs in Final Fantasy XI, usually when your character level reach 30 there will be a quest to obtain some different advance job. But as you may know this advance job isn't more powerful and overpowered than the basic jobs, they only have some special skill that will help other party member in hunt or leveling. Here was some list of Advance job quest in Final fantasy XI.
The quest to obtain Paladin is easy. It was given from the NPC Balasiel in south San'Doria. He located on the bridge. The first thing, you need to give him is a foot. This foot obtained from most of undead enemies. Then you have to go to the Ordellas cave in La Thine. Go to location (G-7) and there will be a small pool. Touch the marks, then touch another marks, which is located not to far from the pool. The spot to touch the marks, is about 15 - 25 steps (depend on your race) from the pool. You will receive an item if done it correctly.
Last back and talk to Balasiel, then talk to the guards on 2nd floor at the guard post east and west Cahaurme(J-9) & Baurise(H-9). Then go to Davoi (E10) and examine the discussed well and get an item. Go back to Balasiel and you will get a Lv 28 Kite Shield, and now you can change your job to a Lv. 1 Paladin.
The quest to be a Dark Knight is an easy one. You can do it as a lv 1 warrior if you wanted(as long as you have lv 30 in another job). However, you must be a warrior to do the quest. That does not mean you have to be a lv 30 warrior, it just mean you have to complete the quest having warrior as your main job.
Talk to Gumbah (Bastok Mines J-7)get the quest. Then go to the 3rd floor of Palbrough Mines (G-8). Get on the ship back to town and after the ride in the Zerhaun mines you'll recieve a 2 handed sword called the Chaos Bringer(?). Equip the sword and kill 100 of any type of enemies without leaving the area. After the 100 or more kills goto the person named Beadeaux located at the Southeast exit of the Pashhow Marshland and you get Dark knight. Now start working on your lv 1 Dark Knight. Dark Knight is, in my opinion, the coolest
Talk to Dietmund in Lower Jueno (G-11). He will come out as soon as you open the door. Wait until it is nighttime (20:00-04:00). Go to a edge of the cliff in Qufim (F-8). Follow the path down the cliff to the edge. At the bottom, click on Night Flowers which will be glowing white like they do at night time. Go back to Dietmund, then talk to the chocobo house owner (Brutus) at Upper Jeuno to obtain the Beast Master job.
Talk to Perih Vashai in the Windurst Woods (K-7). Go to (L-10) of Zoromugh Hills. Wait until the Old Sabertooth dies naturally and click on the Tiger Bones. Take the item you get from the bones to Perih Vashai and he will give you the Ranger job.
Talk to Mertaire, Bki Tbujhja, Ruslan and Tuh Almobankha in Lower Jueno. Then go to to Mhaura and buy a paper from Pikini-Mikini at a Warehouse (G-9). The paper will cost you 500 gil. Get out of Mhaura to Buburimu and head to location (G-9). You can get there through a cave from the main beach. You will find a Song Rune. Click on song rune and trade the paper to the Runes. Then go back to Mertaitre in lower jueno. Then go to Valkurm Dunes and at the northwest point you will see a secret cave, pass through and you will end up at a beach. Find another Song Rune there. Click on the Song Rune. After the cut scene you'll recieve some gil and obtain the singing Bard job. I dont want to see another song rune again.
Speak with Jaucribaix in Norg. He wants a branch from a tree in a sacred place and iron filings from a bomb. Talk to Ranemaud to receive a sacred tree sapling. Now, talk to Aeka to receive old iron from the east. The next two parts can be done in any order.
Trade the old iron to the point at the far west of Konschtat Highlands (D8). A bomb enemy, Forger, will appear. Kill it and you will receive the iron fillings. Even if you fight this bomb with a party, it will only drop 1 item, and you can only trade iron every 3 minutes.
Use an axe at the mark point on the huge tree at the west side of The Sanctuary of Zi'Tah. A Walking Tree enemy, Guardian Treant, will appear. Kill it and examine the mark again to receive the branch.
Return to Jaucribaix with these items. After you give him them, he will tell you to come back in three days (3 hours). Come back and you will receive the Samurai job class and an Unsigned Sword. You can now change to Samurai in your Mog House.
First, go to "Cargo Room A" (I-10) in Port Sandoria. Then speak to Arminibit and Ceraulian. Enter the Chateau d'Oraguille then down the path at (I-8) to Bostaunieux Oubliette. Enter the first path that's to the right to meet Novalmauge. Go to the Cathedral in Northern San Doria(L-7) and speak with Morjean to recieve the quest from Oiheaurese. After receiving the quest, go to the Auction house and buy some Pickaxe for excavating purpose.
Now head to the Maze of Shakrami to excavate at the "Excavation Point" (G-7),(I-6), etc., not "Fossil Rock", for a "Dragon Egg". Go back to Cathedral and speak with Morjean. You should then accept the quest given by Yachemidot. Go to the Meriphataud Mountains. To the east at (K-8) will be the end of the Drogaroga's Spine. There will be a npc there.
Trade the egg to the npc and an event will occur. Go back to Sandoria and enter Chateau d'Oraguille. Then enter into Royal Knights' Quarters(H-9) and speak to Rahal and receive a key item. After receiving the key item, go to Ghelsba Outpost. Locate the "Hide Door"(G-10) in the Ghelsba Outpost and defeat the Dragon. The daron is behind the dorr, and only one party can fight it at a time. Bring a good party(6 people)of lv 45s to take it down.
To start off, you need to talk to Kaede in a house located in Port Bastok (I-5). Then head into the warehouse in Port Bastok (F-5) and speak to Kagetora. Go back to the house where Kaede is (I-5), and goto the room to the left. In there you have to speak to Ensetsu. Now go to Bastok Mines. Then go to Zeruhn Mines, and then to Korroloca Tunnel to (A-9) and you'll be transferred over to (N-8) on the same map. Now head over to (G-8) then you'll be transferred over to (I-11) of the same map. Now head over to (K-8) and there will be a mark.
Get ready and click on it to fight 3 Korroloca Leech (Leech type NM), You may want to clear the area of Thread Leech's since they will start attacking you if they see you are fighting the Korroloca Leechs. After the fight click on the mark to recieve a key item. Now head back to Ensetsu in Port Bastok (I-5) and head to the new area Norg and speak to Ryoma to complete the quest.
To get the summoner advanced job, you first have to go to Windurst Walls (G3). When you get there, talk to the taru Ajido-Marujido. After that, go kill any kind of leech creature that you want. You have to get the Ruby from it, but you will only get it as a drop if your level is above 30. You have a small chance of getting it quickly (1% drop rate).
Now goto the House of the Hero in Windurst Walls. Investigate the door with the stone in your item list. After that, experience the 7 different weather conditions. You only have to have the weather effect on your map. You have to experience areas that are Pleasant, have Fire, Ice, Earth, Water, Wind, and Lightning, but not all at once.
After you have experienced those elements, head to La Theine Plateau. There is a stone circle there. Target and trade the stone into it. You will now obtain the Summoner job and your first summon which should be obvious after the quest.
Source(s) : IGN faqs