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.