Dont get frustrated if you have to do certain steps over again. It happens to me every time.
One thing I would do, if I were you. Wait to put the power supply in until last. Sometimes its hard to get the heatsink installed on certain motherboard/case combos if the PS is already there. Plus, not having all those wires hanging in the way makes it alot easier to see what you are doing. The PS is one of the easiest and most straightforward computer parts to install, so there's no reason to have it in the way too early.