1) Never work for someone else for free. You have skills, make sure you get paid for them.
2) Avoid religious fanatics. This includes (but is not exclusive to):
Scrum is the only One True Development Process people (be Agile and let your project dictate the process, not the other way around)
The Object Oriented Programming is the only way to develop crowd. The Cache is King, polymorphism and poorly laid out classes kill it. By extension the patterns crowd where they have a hammer therefore the world is a nail.
3) Avoid people tied to a specific technology. Primarily game engines. You don't always need a game engine to create a game. Opinion here, but I think that the reason why we, as gamers, have not seen any really revolutionary type stuff in the last 10 years or so. Producers are so risk adverse that they are dictating certain technologies thinking they are going to save time (i.e. money) but end up with a sunk cost fallacy.
4) If you are hired by a development house realize that you are a mercenary, companies will not be loyal to you and you will end up in a Death March and not be paid appropriately and typically dumped when the project is cancelled or 'finished' and shipped.
5) Avoid Brogrammer culture at all costs.
6) Don't worry about code reuse, you probably won't reuse code. You will learn stuff and figure out how to do it better the next time.