You'll be reading textbooks, journal articles and conference papers.
Start by reading the "classic" papers in your field.
A Ph.D. student will read paper drafts in later years.
You may find published bibliographies for your area (e.g., computational geomtry)
I also suggest browsing the library for a couple of hours late on a Friday afternoon just to let new ideas pop into your head.
When reading a paper (from [d, sction 3.1]:
First skim the paper to get an idea of what it is about, without investing days in understanding notation or filling in background material
If it is still worth reading, reread it carefullly.
Make a notation list while reading.
Some questions to ask:
Are you reading buzzwords and jargon or deep ideas?
Is this paper a small increment in knowledge or a new idea?