I found this this post at the right time in my career, a lot of new, increased work ...
Clarify your priorities
As you start to see projects pile up on your desk, or even if there was an official meeting where you were tasked with taking on the responsibilities of an open position, take some time to talk one-on-one with your manager. Figure out what tasks are really priorities and what will just have to wait until you have more time.
This can be a hard conversation to have with your manager or even with yourself. To start, here are a few questions to consider inspired by Business Productivity:
What projects will have negative consequences if we put them off?
What projects will give us the biggest return if we tackle them now?
What are the long-term projects that can be done slowly over time and what are the short-term projects that require immediate attention?