You might feel overwhelmed, but as a newbie always say yes if someone asks you for coffee, to lunch, to volunteer on a project or just about anything else. 

Take initiative, look into why things are done the way they are, and take everything as a learning experience. You need to master the field before you start making suggestions.

It doesn't matter where you are in the pecking order or where anyone else is. Treat everyone with the same high level of respect, from the entry-level employee to the CEO. You never know who could have your back, do you a favor--or even be your undoing.

As a newbie, you need to work harder than anyone else. You need to prove you want to be there, you like to be there, and you'll give it your all.

Make it a point to repeat everyone's name after introductions, and address them by name whenever possible. You need to drill those monikers into your head.

You might not "get" the weird birthday song yet or why Friday night happy hours are always at the same bar but go along with it. Traditions are important, and giving them a fair shot can help you get integrated.

Chances are your predecessor spent a long time putting together that handbook of Standard Operator Procedures. 

Learn it, memorize it, and live it. It's your cheat sheet. 

It doesn't matter if it's carrying files to storage or helping a co-worker with a spreadsheet. If you can help in any way, do so. That's where teamwork is born.