What would I do or what would Humanity do?
Because honestly I've thought about this, and first contact from my point of view goes one of three ways.
1) They are more advanced then us, we try to look as inoffensive as possible, beg, buy, borrow, steal everything we can from them in a desperate rush to catch up and address the power imbalance, possibly getting ourselves wiped out in the process.
2) They are roughly the same level as use tech wise, we'll attempt to play nice, trade, etc, but we'll likely end up in a war with them over something pointless. Pretty the same way governments work on Earth.
3) Less advanced, we'd end up conquering them, oh we wouldn't call it that, but it's what would happen without a doubt. It would start small "helping" them with little things, but over time we'd own or control everything on their planet.