Cross-References
Cross-referencing tools are perhaps the single greatest bible study aid. This allows you to compare scripture with scripture. They refer you to other passages that relate to the one being studied. The Treasury of Scripture Knowledge is undoubtedly the best cross-referencing book ever designed.
Lexicons and Word Study Books
A lexicon is much like a dictionary. It is an alphabetic listing of major words found in the English Bible giving their Greek or Hebrew meaning. This allows you to get a feel for how the word was used in the days of the Bible. Although a wonderful tool, they can be confusing and misleading. Often a Greek word could have several different meanings. If one is not careful to let the context determine how a word is to be defined the reader can use a lexicon to attach a meaning to a word that the biblical author did not intend.
Two easy to use lexicons are the Vine's Dictionary of Old & NT Words and the lexicons found in the Strong’s Concordance.
Another wonderful study tool is A. T. Robertson’s, Word Pictures in the New Testament. Although it would be helpful to know Greek to use this help, it is not required.