What should I know about Mercurius?

I'm traveling to Europe in the Spring, and I'm in the process of saving up money for the trip. The trip itself is paid for, I just need money for food, transit, souvenirs, etc. but I digress. I figure it would be a good idea to gain favor with Mercurius in the time between now and then, but I'm wary as He's also a god of mischief, trickery, theft, lying, and cheating, which I guess could be a good thing if my personality and past actions are taken into account... yeah.... Anyway, what do I need to know to not piss Him off? Should I play it safe and just leave Him be?