When you have blue buff or a good lane sustain.

Run into the middle of the creep wave like this:


O O O <--Melee Minions
=) <---You
M M M <-- Mage Minions

Then use a R+E, this will be close too, or completely Clear the wave out, or if you don't have the AP Yet it'll do enough just for auto's for the Mage minions.

Then i normally run around the front of them, like this.

=) <--You
O O O
M M M
Then use a Q, clears a whole wave.

Always start with Q and just auto attack for minions, unless you are being heavily harrased by your enemy lane, then use Q to make them back off.

Typically you want around 70CS before you start to do any type of aggression, or until you get blue buff.

Blue Buff is next to vital for Karma, it decreases her ulti cooldown so you can get more megashields up :3

First Buy: Boots + 3 Healthpots
Rush: Hextech Revolver

End Game Items:
Wota = Dem Spell Vamps, really helps for teamfights
RoA = Extra bulk and Mana which is always nice
Sorcerers Boots = Can be changed for Merc Treads if need be, depending on if your a passive karma or offensive.
Abysall: MR and AP aswell as the MR debuff Aura
Zhonya's: Armor for dem AD Carries, and use the Active if your being focused or need to wait for a Manta boost buff.
Rabadons = AP

Max Q asap, followed by E, Level W as if it was your ultimate, it's not really useful unless you need to run or slow enemies down, but you can use it for offensive if one of your team-mates are infront of the team, just pop W for a quick burst.

Throw a W onto your fight starter, Skarner, Jarvan ect and let them do damage with the W and the speed boost, then if your quick use R and E for a megashield and TONNES OF DAMAGE, then Q for more AoE.

After that quick burst, you play a more supportive champion when you use R+Q for keeping carry or tank up, or if the fight is going well, use R+E for TONNES OF DAMAGE.

Priorities on Manta

Mid: Q, for heals until i get my E

Ganking: E to deal damage and shield anyone low, or if their a quite high hp bot lane, a W to slow them.

Team Fights: E and Q, but normally i focus on E

Pros: Massive Damage, Amazing Slow, and Healing powers.

Cons: Very weak late game, when she hits around level5 she will start to dominate the lane