CNJ/WHM

White mage

As a white mage you are a healer. Until you get better spells

Cure

Is your bread and butter. You will cast this spell more than any other in your career as a white mage.

Protect

Is something that should always be on your party. This spell reduces the damage taken by party members, and every little bit helps.

Stoneskin

This spell rocks (pardon the bad pun) it's essentially a 10% increase in the targets health. The more health the bigger the effect.

Regen

You love this spell. Before this your mana is much more limited. Use it.

Medica II

Full party Regen. You love this. Use it.

You have a couple hot water buttons as well, namely

Presence of mind

Faster casting. Saves lives.

Shroud of the saints.

Heals pulling off the tank? Not any more.

(Fix more later)

Couple things, from the side perspective of a SCH.

Medica II: You can't afford to spam it, your MP isn't there for that. Keep it sparse unless you are in a state of constant emergency or the battle's almost over.

Protect: Always remember to recast after a res or two, unless you know that person just got unlucky and isn't likely to be hit again before the current engagement is over.

Stoneskin: You aren't a SCH. Don't put up stoneskin mid-fight unless you're in a lull and it's on the tank, unless this is a full party duty and the other healer is taking care of all the damage before you can even get to it.

Regen: Try not to have it active on a tank as they go to pull another group if they're a pug. You can never be sure if they're going to be quick enough on their lead flash/Overpower to keep you from getting murdered with the agro that'll generate on the non-lobbed enemies in the group.

Cross Class: Swiftcast is essential. Get it ASAP. You don't have to have it as your FIRST cross class as it's mostly going to be used for rez and lower level duties you might not need it as much. Other healers, followed by Summoners and Tanks should be the first thing you rez if there are multiple party members down, assuming this isn't a situation where you're the only one alive. Then you may need to bring up a tank first. May.

That's all I've got for you for now, I'll probably make a SCH guide later.... Not today. This post has been enough homework-blowing-off.