First Patriarch Problems

[Genesis 13:1-5]
It sounds like they had been journeying for quite some time. I'm sure this was still some awkwardness about the whole Egypt incident, and that Sarai was probably going to hold that over Abram's head for the rest of his life any time she wanted to buy something expensive. But since spirits were getting low, they all traveled back to the altar that Abram had set up when God promised him the land and they did some praying there.
In addition to thanking God for something the moment He promises it to you, it's also wise to do like Abram did and set up a reminder of it. Abram built an altar, but your reminder can be as simple as writing it down somewhere and keeping in a notebook, or in your wallet, or taped to your mirror, or as a reminder that pops up on your phone once a day. When it seems like life is taking forever and that the promise is never going to happen, go back to that marker and cry out to God. If we look at the prayers of people like king David in Psalms, God's not afraid for you to ask questions about what in the world is going on.

[13:6]
"God gave me land, but my brother and I are so rich that it's not big enough #ChosenOneProblems"

[13:7-9]
It was a bit cramped in Canaan, and there was starting to be some sheep fights or something. Abram really doesn't want their employees squabbling amongst themselves, so he offers to split the land up. He gives Lot first pick of the land, and promises to go settle the opposite direction from where Lot goes so they can give each other some elbow room.
In-fighting is one of the quickest ways to kill off any movement. When people are starting to squabble amongst themselves and unity is starting to degrade, it needs to be nipped in the bud immediately. I read a book on theater directing which stated that if someone is damaging the unity of the group, they need to be fired immediately regardless of how talented they are. Abram saw the team spirit starting to fall apart, and he did the right thing as a leader and decided they needed to give each other some space. I'm sure it was tough, since they had all assumed they were in this together, and living on opposite sides of their land was probably not in the original plan. But unity is the most important attribute for any team, and it needs to be preserved at all costs. Even if this means some members going their separate ways, it's better than the entire operation falling apart.

[13:10-13]
Lot got first choice of the land, and poor Lot made a really bad decision. The land was nice, and there was a city nearby so he could make a Costco run when he needed to, but unfortunately it was home to a group of people that have the distinction of being the only people after the flood that were so screwed up that God just nuked them. That hasn't happened yet and I'm sure Lot thinks he's gotten off pretty well, but it will turn out to be a decision that comes back to bite him.

[13:14-18]
And Abram gets the rest of the land. God also takes this moment to tell Abram exactly how big this nation of his is going to be: really stinking big. More than can be counted.
It's interesting that God waited for Lot to be gone before delivering this message. I have two possible interpretations of it and I'm not sure which one is more accurate.
First is that God waited until now because Abram had just decided to settle down and his territory was now official, so God could reveal the next step of the plan. After spending some time journeying around, Abram had finally come back to where God said He was going to be in the first place and decided to take a stake in it, so God could start the next phase. In this case, the lesson is that, even when you don't know the long-term plan, if God has told you the next step, you need to pitch your tent and make it official. While you're still journeying around trying to figure stuff out, God's not going to show you what's next. Pitch your tent in the land He's promised you, and He'll go from there.
The other thought is that getting rid of Lot was what allowed God to reveal the next step. It could be that Abram was never supposed to bring Lot in the first place, and that finally settling down with Sarai and going it alone like he was initially told was what triggered God revealing the rest of the plan. In this case, when God tells you something, don't change the terms. Abram putzed around for quite a while before heading out with just his crew, and probably wasted a good deal of time. When God tells you to do something, then do it, and do it completely.