Day 2: Get a job
If you've played other Final Fantasy games, chances are you've run into the "job system." It's a classic - it lets you totally change your character's class and abilities. Even better, once you hit level 18 you can equip a "Support Job" to make your character kick even more ass, with a sackful of new abilites. In total, Final Fantasy XI sports 18 jobs, each more classic than the last.
Support Jobs operate at half the level of the main job, but can alter your game plan greatly. It's like this: a level 75 Black Mage can use the spells and abilities of the White Mage class up to 37. It's important not to get behind on your Support Job's level. Not only will you miss out on choice abilities, but other players who want to party for experience points won't invite you along.
All jobs are leveled separately, so when you change to a new job you'll drop to level 1. The good news is that the levels in your other job won't be lost - if you decide you liked being a Warrior more than a Puppetmaster, just switch on back. When changing jobs, combat skills from your previous job will carry over. This means you can still whoop ass - and level your new jobs that much faster.
Twelve of the 18 jobs are "Advanced" jobs. That means you can't pick them from the beginning of the game. They must be unlocked by completing a certain quest - once your character hits level 30. So why are we telling you this now? Because you'll want to start levelling one of the recommended support jobs now - and take it to level 37 before you switch to something more advanced. You'll save time and money. It always counts to plan ahead.