I'm starting off my lectures on the Pentateuch for another year tomorrow. Perhaps surprisingly, I like to start off near the end of Deuteronomy instead of at the beginning of Genesis.
Why? Well, there's a verse near the end of Deuteronomy that I think is very helpful to students who are about to dive into Genesis:
The secret things belong to the LORD our God, but the things that are revealed belong to us and to our children forever, that we may do all the words of this law. (Deut. 29:29)
Genesis is a hugely important book, but it is also one where people find it very easy to get distracted. When teaching Genesis, I know I'm going to get lots of questions about science (and dinosaurs; they always ask about dinosaurs!) and other issues which are not the main focus of the text. Now, I'm not suggesting that we can't learn anything about science from Scripture; as the inerrant Word of God, everything that Scripture says is true, whether it be theology or biology. However, science tends not to be the main point of the text. That means that by focusing on questions of science, we miss out on the real issues with which the text is dealing.
God has revealed everything that is necessary for our salvation and godly living in His Word. But there are also some things he hasn't revealed (such as some issues about dinosaurs!). The things that He hasn't revealed aren't necessary for us to know, even though sometimes we might really want to.
What we need to do is focus on what God has revealed, learn from it, and live in light of it. If that's what we're doing, then the secret things will bother us less and less.
Keep the focus on what God has revealed. Genesis is not intended to lead us into speculation, but rather to reveal to us our sovereign LORD, His dealings with Man, and His promised salvation. Let's not lose the riches of Genesis to unprofitable speculation. Don't get distracted!