If for some strange reason you want to pursue graduate work in Biblical Studies, you will do well to heed Mark Smith's exhortation (HT: Charles Halton) about the importance of reading primary sources in the original languages. You will also need to cultivate an awareness of the field--which is to say, start devouring important books by major big-picture scholars who know how to write well, and begin as early as possible. (My colleague Eric Ortlund's OT Reading List is a great place to start if you are doing OT. Does anyone know of similar NT reading lists online?)
To be sure, the primary literature is most important, and the secondary literature--especially commentaries--can be overwhelming, frustrating and distracting from the whole point of Biblical scholarship, which for Christian scholars should, arguably, have something to do with the Bible. But good, seminal secondary stuff, at its best, gives new eyes for familiar texts.
If you are wondering why pursuing graduate work in Biblical Studies is strange, consider Carl Trueman's Minority Report in the latest issue of Themelios. I was glad to find him echoing my own more limited advice.