How we cite our quotes: Act.Scene
Quote #1
Lodo. I am ever bound to you.
This is the world's alms; pray make use of it.
Great men sell sheep, thus to be cut in pieces,
When first they have shorn them bare, and sold their fleeces. (1.1.)
"Great men" here (and elsewhere in the play) are way different from good men. A "great man" is just a powerful man, in Webster's world—someone who won't hesitate to betray and destroy his underlings for profit.
Quote #2
Fran. Do not fear it:
I 'll answer you in your own hawking phrase.
Some eagles that should gaze upon the sun
Seldom soar high, but take their lustful ease,
Since they from dunghill birds their prey can seize. (2.1)
Francisco means that he's the eagle and Brachiano's the dunghill bird. Although he has better things to do, he might come down to Brachiano's level, if only to defeat and punish him for his adultery.
Quote #3
Conj. Sir, I thank you.
Both flowers and weeds spring, when the sun is warm,
And great men do great good, or else great harm. (2.2)
The Conjurer seems a little hesitant about what he's doing. He's using his magic to let Brachiano see the pair of murders he ordered—but he seems a little skeptical about Brachiano, who is definitely one of those "great men" doing "great harm" as opposed to "great good."