alternate picking is consistantly picking down up down up the whole time. economy picking calls for you to always use a downstroke when changing strings downward and always pick with an up stroke when going up.
Alternate picking: strictly up/down movement with the right hand.
Economy picking: like alternate picking, but don't change directions when moving from string to string.

IE, if you're moving from the G string to the B string, you should be using a continuous downstroke for both notes.

Economy picking is kinda like the bastard son of alternate picking and sweeping.
Alternate picking straight up and down ever time no matter what.

directional picking is alternate picking when picking on the same string for more than two notes, but if you change to a string then you "sweep Pick"

ex. lets say you have to play 4 notes on one string and one note on another string, the one under it. this is what you would do using alternate picking and what you would do using directional picking.

Alternate picking- up down up down on 1st string followed by a up stroke on the other string.

Directional picking up down up down on 1st string followed by another down stroke on the other string.
Quote by IclaptonisgodI
there is emotion in metal but, its "im angry!!!!!!!!!!!!!!!!! and u should be to"

"sometimes i think it's better to fight a false sense of intelligence with a false sense of stupidity"
theoretically economy picking is better because you should be able to go faster and cleaner because you are travelling the shortest distance. But alternate picking is just as good if you are good at it. I am self taught and when i learned to pick I learned economy picking without even realizing it which is kind of awesome. Whichever you feel is the best will work just fine.
Quote by Ht666
Does anyone know any good exercises that help you get better at Economy?

I'd sweep up and arpeggio and then pick the scale going back down. And then Pick up the scale and sweep back down. Try that.