Would you guys help me with my first couple shoot for a friend ?

So, few weeks ago I was at a gas station taking photos of passing cars when a guy on a motorcycle stopped nearby. I asked if I could take some shots — he liked them, asked to use some of my other pics for his finals project.

Now he asked me to do a shoot of him and his girlfriend with their bikes. I’ve only done something like this once, but he was really okay with the fact that I'm a beginner. We’re meeting next weekend and I don't want to disappoint him since he was do kind :)

I want to keep things spontaneous — have them interact with each other, walk around the bikes, less posing, and do some "moment" shots ( snapshots? english isn't my first language ) since he liked them and those pictures are my favorite.

I have a few ideas but I think I need some advice.

Do you have any tips for shooting couples ? Composition, posing ideas, things to avoid etc. ?

Thanks in advance :D