Fugitive

4:12 When thou tillest the ground, it shall not henceforth yield unto thee her strength; a fugitive and a vagabond shalt thou be in the earth.

More tough farming.  And: fugitive and vagabond.

I can't say I understand either of those two.  To me, a fugitive is someone who is running from punishment, not as punishment.  And vagabond means either that you choose to keep moving around (and choice isn't a punishment); or that you can't find a job (or food) where you are, so you keep moving around.  Not being able to get enough food farming might be what's going on.  But I don't see how moving around is going to help if you're cursed by God.

Mouth

4:11 And now art thou cursed from the earth, which hath opened her mouth to receive thy brother's blood from thy hand;

This cuts straight at his livelihood.  Of course, he's a murderer, so perhaps that's ok.

Again, this is clearly not literal: "opened her mouth".

Blood

4:10 And he said, What hast thou done? the voice of thy brother's blood crieth unto me from the ground.

Is God still unclear on what happened, despite hearing the blood?  Or is this more chastising?

The last half is pretty awesome, especially if you imagine it spoken by Dracula.

Keeper

4:9 And the LORD said unto Cain, Where is Abel thy brother? And he said, I know not: Am I my brother's keeper?

I can't tell if God actually doesn't know what happened, or if he's still taunting Cain.

Cain doesn't seem like a good person: he's a murderer and a liar.  It's a wonder God doesn't get along better with him.

Talked

4:8 And Cain talked with Abel his brother: and it came to pass, when they were in the field, that Cain rose up against Abel his brother, and slew him.

Basic storytelling seems to be breaking down here.  What did they talk about?  Did Abel say something incredibly obnoxious (that is, God-like)?  I thought you were supposed to talk to people to work out your issues, not as a prelude to violence.  Does this have anything to do with the desire bit from the last verse?

So, God incited the first murder.  First, by demanding offerings for no reason.  Second, for insulting some of the offerings for no reason, while praising others.  Third, by mocking the one whose offering had been rejected; and by blaming him.  This seems all crafty and subtil and evil of God.  Also, sort of pointless.

Lieth

4:7 If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him.

This apparently is God talking.  And, to clarify our doubt from the last verse, he pretty clearly seems to be taunting Cain.  Specifically, he is blaming Cain because God didn't like the offering Cain made, which was pretty much what Cain had to offer.  So how was that Cain's fault?  He should have chosen a different profession, because he should have better offerings.

I have no clue what the last sentence means.  This sounds like the bit from 3:17, where Eve's desire was to Adam and he ruled over her, only inverted.  He's talking to Cain, so it seems like Cain should be doing the ruling.  But it doesn't really make much sense.  Who is the other person?  Abel?  Abel's desire is unto Cain?  That's pretty bizarre, but perhaps it's par for the course for this warped God.

Fallen

4:6 And the LORD said unto Cain, Why art thou wroth? and why is thy countenance fallen? 

There are two options here.  One: God has no idea what happened.  This would make him at least insensitive, if not outright stupid.  Two: God is further mocking and provoking Cain.  This would make him downright mean and childish.

Wroth

4:5 But unto Cain and to his offering he had not respect. And Cain was very wroth, and his countenance fell. 

I'd be wroth, too; wouldn't you?  I think that wroth means "pissed off".  And "his countenance fell" means "he looked sad."

Ok, Cain grew fruit and Abel grew sheep.  And Cain offered up to God some fruit and Abel some sheep.  Why they made offerings to someone who so badly mistreated their parents is one question.  Regardless, they clearly offered what they had to offer.

God, that day, was apparently not in the mood for fruit.  And he was rude about it.  No explanation is given; the only option we have is simply assuming that God was being a jerk or a troublemaker.  And he mistreated Cain, which seriously bummed Cain out.

Firstlings

4:4 And Abel, he also brought of the firstlings of his flock and of the fat thereof. And the LORD had respect unto Abel and to his offering:

Because who wouldn't want some young sheep fat?

Offering

4:3 And in process of time it came to pass, that Cain brought of the fruit of the ground an offering unto the LORD.

I don't understand the whole concept of offerings to God.  Apparently I'm not alone; the practice seems to have died out.  Cain's giving God food because God's hungry?  Because God is wildly insecure and needs gifts to feel good about himself?

And Cain is grateful to God because God made farming difficult?  Because God made snakes bite Cain's heels?

The open phrase is a very windy version of "eventually".  But it wasn't necessary to point out the passage of time between Cain and Abel being born and them getting occupations.

Tiller

4:2 And she again bare his brother Abel. And Abel was a keeper of sheep, but Cain was a tiller of the ground. 

What, no computer programmers?  Did Cain start tilling when he was an infant?

Anyway, still agricultural.