What would be good resources for improving my skills in writing about literature?
There are two things which correlate very strongly with student skills in writing -- how much leisure reading (i.e. reading not assigned for school) students do and how much writing they do. So your first strategy should be reading literary works in addition to those assigned in school to get a stronger sense of historical periods and genres.
For literary interpretation, read literary criticism. Think of various critical schools as resources for interpreting literary works, giving you starting points for different methods of interpretation, including typical topics to address, questions to ask, and technical terms to use.
The Purdue OWL (cited below) is a useful online resource.
personally speaking, i read novels. and i literally read every criticism over the Internet regarding my syllabus. reading authentic critical analysis helps a lot. it guides you on how to adopt a mature style of writing. and thirdly you should improve your vocabulary. i have a small dictionary of my own. like i have written meanings of words that i find difficult and i go through them every Friday. 2 pages minimum is also more than enough as long as you absorb it and then use it. unless you wont employ that style or vocabulary, you wont be able to produce good answers.