http://ffxi.allakhazam.com/db/guides.html?guide=381
That should help get you started.
Note however that the game is mostly dominated by /ja and /ma. Other things like /nin /blu /sch or what have you are usually compatible by just using /ma, making knowing all the other little acronyms for job specific spells rather useless.
Another very useful command is:
/target <bt>
This will imeadiatly focus your target on the enemy that is currently in red, and is useful if you play a mage job that would constantly be switching targets from the enemy to the players. For ease of use, always have this on the same number for every sheet in your macro book you use. For example, i always have it on ctrl+8.
There's also <stnpc> and <stpc>
npc stands for Non-Playable Characters and PC stands for Playable Characters. NPC's are green named citizins of Vana'diel, or the monsters your trying to ruthrlessly murder. PC's are anyone that's controlled by a human. It doesn't not mean personal computer in this sense.
ST, to my knowledge, stands for sub-target, which is like your regular target, but it's a blue arrow instead. It's useful because it allows you to unlock your current target (as a mage you typically won't be locked onto a target, which is when there's a red line around your target box and you begin strafing around and such when you have them targeted in this fashion) keep it as a target in your window, but choose secondary targets for your current effect.
For example, rather than have a cure macro for <p0> through <p5> just use one cure macro that would look like this:
/ma "Cure" <stpc>
Now you can stay focused on little Timmy the tank, but cure the Samurai who just get hit with a nasty AOE. Also you just saved about a bajillion macro buttons, which really makes you more fluid on the battlefeild.
Also, if your'e going this route, I typically like to add recast to the spell. It works like:
/recast "Stone"
This will prompt a yellow text by default to come up in your chat window saying something along the lines of Stone "00:08" meaning it has eight seconds to go. I find this useful because it 1) Let's me know when I can cast this spell again and 2) Gives me one last chance to see that I selected Firaga III instead of Fire III. Since your using a the stnpc or stpc command, the spell doesn't fire off right away leaving you and your part screwed if you happened to fly by one sheet too many.
One last tip, try to organize your macros in a fashion so that your sheet's all have the same *type* of spells on them. For instance, I typically have my alt line full of whitemagic specific spells. The first sheet is the cure's and curaga's. The second is the na spells and some buffs. The third might be summons and what not. Then my ctrl list is offensive spells. The first might be direct damaging spells like stone, blizzard, fire ect. The next might be enfeebles. I also set up the spells so they go in an order of which spell would be the next spells weakness, which helps cut downtime on memorizing the elemental wheel when you start out. For instance /ma "Fire" <stnpc> would come before /ma "Blizzard" <stnpc>
There are however certian spells like stun, probably the most critical spell in the entire blackmage arsonal, that must be treated like the /target <bt> macro. Stun is typically on my ctrl+1 key for every row.
That's most of what I can think of that's not generally listed that I found exceptionally useful. if you have more questions feel free to ask!