I recently starting playing Guild Wars again after a lengthy hiatus, however, I can no longer recall how I change my secondary profession.
How can I change my secondary profession?
The requirements for changing your Secondary Profession are different, depending on which campaign you do it in and from which campaign your character originates. I'll be linking to the official Guild Wars Wiki, as it's an invaluable resource that isn't at risk of going going down anytime soon, and anyone playing the game should use it judiciously, as there's a ton of information.
I'll refer to campaign characters as coming from their continents of origin, so it will be as follows:
In addition to acquiring the ability to change your Secondary Profession, you will also be allowed to enter the Realms of the Gods, aka The Underworld and the Fissure of Woe, which are elite areas in the game. You must be Ascended in order to enter these areas (in addition to the world needing the Favor of the Gods and having to pay 1 plat to enter).
Characters are allowed to complete the ascension quests of other continents, but some may not receive the benefits of Realm of the Gods access and Secondary Profession changing. I'll outline that further on in each campaign section. Ascension with a capital "A" refers to Tyrian Ascension specifically, while lowercase "a" ascension refers to the process of acquiring those benefits.
A note about running: It's not uncommon in Guild Wars to have people run you places for ingame money (platinum, commonly abbreviated as "plat"). This involves having people use specialized movement speed builds in order to get you from one outpost to another, skipping the usual order that you would take to naturally complete the game. As I am neither a runner nor do I have people run me places, I won't be taking running into account for these comparisons, but you should know that it is an option if you choose to do so. Going rates vary though, depending on which route you're paying for, how long it is, and whether or not patches nerf builds, so you'll have to do your own research on that.
Acquiring Ascension benefits in Prophecies takes the most amount of time out of all the campaigns when comparing how long it is from rolling your character to how long it takes to get to the missions you need. Prophecies is also the slowest paced of the 3 campaigns. You will be stuck with your current Secondary Prof for about 2/3 of the campaign.
Location in storyline: The 15th-18th out of 25 missions. They're located in the Crystal Desert. You're transported to the major outpost there, Amnoon Oasis after completing the Sanctum Cay mission.
There are a few quests/locations that you can only get access to if you complete the above 4 quests for Tyrian Ascension. These include:
In Prophecies, after completing Augury Rock, you can do one of two things:
Alternatively, you can complete your choice of 4 of the 6 missions (obviously the ones for your current primary/secondary are excluded) to unlock the various secondaries for free. These are located in the following outposts in the Crystal Desert area:
The path you choose to take depends on which you value more, your time or your money. The quests aren't necessarily super long or difficult, but you do need to have access to the various outposts, which requires running around and opening them up.
Factions is the fastest paced campaign where you'll hit level 20 before leaving the starter island. People who level PvE characters and don't want to wait until getting through Prophecies to be able to access the Realms of the Gods will often travel to Cantha to become Weh no Su.
Location in storyline: The 4th of 12-13 (number is variable because the story branches at one point, but you can go choose to do the other mission if you want) campaign missions. You arrive here after completing the Vizunah Square mission, then the Finding the Oracle and Closer to the Stars Primary Quests.
The pace of Nightfall falls in between Prophecies and Factions, but you still get access to Secondary Professions much earlier than Prophecies.
Location in storyline: Received after Consulate Docks, the 4th of 18-20 missions (like Factions, the story branches, so some missions are optional).
One thing some people don't notice is that you do not need to revisit Profession Changers to change your secondary again if you already have the profession unlocked! When you are in an outpost, simply open your Skills window (K by default).
Simply click on this highlighted area and it will open a dropdown for you to choose from the various Primary/Secondary profession combinations you have unlocked.
This doesn't require any quest completion. You can change these at any time in an outpost (the same way as above) to any Secondary that your account has access to. The requirements are: - Prophecies for the 6 core professions, Warrior, Ranger, Monk, Elementalist, Necromancer, and Mesmer - Factions for Assassin and Ritualist - Nightfall for Dervish and Paragon