When it comes to carrying out the work, it's really important that you keep an open mind and approach all tasks with enthusiasm. Try to recognise the learning opportunity in everything you do, including the more menial or administrative tasks (this applies equally to the early stages of graduate roles). If your first task is to proofread a long, complex document, don’t simply sulk and act as if the work is beneath you. Instead, be thankful that the task isn’t beyond your capabilities, maintain a positive attitude and be as helpful as possible. 

Try to focus on the fact that you’re receiving potentially valuable exposure to an unfamiliar document that you may one day have to draft yourself. You could also use the opportunity to ask questions about the context so that you can learn more about the document and how it fits into the bigger picture. This is the mindset that firms will be looking for. It’s all part of the learning process. After all, it’s better to have the opportunity to do a solid job on an administrative task rather than being thrown in at the deep end and screwing up a far more complex or substantive task. Plus, the next time you come across that document, it will seem more familiar, meaning you will likely be far better placed to take on a more substantive role (without screwing up!).