My reading

1. Joseph's dreams
2. The selling of Joseph
3. Judah and Tamar
4. Joseph and Potiphar's wife
5. Joseph in prison
6. Dreams of the cup-bearer and the baker

From the very first line of the haftarah we can see its connection to the parasha:
"Thus said the Lord: For three transgressions of Israel,
For four, I will not revoke it:
Because they have sold for silver
Those whose cause was just,
And the needy for a pair of sandals" (Amos 2:6).
Although the prophet is railing against the people for exploiting the poor and the helpless, his words resonate with the original sin committed by Joseph's brothers, who sold him into slavery "for twenty pieces of silver" (Genesis 37:28).
Was Joseph actually a "tzaddik"(a righteous man), as he is called by the sages, who point to his ability to withstand the overtures of Potiphar's wife as proof of his righteousness—for it was not easy for him to refuse her supplications? They say that even before Potiphar's wife clung to him, he had begun to curl his hair and adorn himself with ornaments (Tanhuma Vayeshev 8). In Sota 36b they claim that Joseph and Potiphar's wife were about to make love, but Joseph reneged at the last moment, because he saw his father's reflection in the window. He dug his fingers into the earth and refused to climb into her bed. Given this description, Joseph was not a perfect human being who was never troubled by darker impulses; on the contrary, he was a man who constantly struggled with temptation and only at the last minute was able to save himself.*
Joseph treated his employer, Potiphar, fairly. For Amos, justice—or righteousness, "tzedek"-- is the supreme value. A society that is not grounded in justice has no right to exist; it will be punished and will disintegrate. This is the danger facing the people of Israel because of the unjust way they treat their weaker members. Selling the tzaddik was not the only sin perpetrated by those
"who trample the heads of the poor
Into the dust of the ground,
And make the humble walk a twisted course.
Father and son go to the same young woman
And thereby profane My holy name;
They recline by every altar
On garments taken in pledge,
And drink in the House of their God
Wine bought with fines they imposed" (Amos 2:7-8)
It is just because of the special relationship between God and Israel that He demands of them a higher standard of moral behavior than He expects from other nations. The punishment for failure to meet that standard will also be harsher:
"Hear this word, O people of Israel,
That the Lord has spoken concerning you,
Concerning the whole family that I brought up from the
Land of Egypt:
You alone have I singled out
Of all the families of the earth—
Therefore I will call you to account
For all your iniquities" (Amos 3:1-2).
Just as Joseph withstood the temptation of illicit sexual relations and was faithful to Potiphar, so, too, is the nation of Israel called upon to withstand the temptations of greed, injustice and desecration of God's name, and to deal righteously with all its members.

* Thanks to Rabbi Yaron Ben David, http://www.beerot.co.il