There are a countless Bible commentaries to choose from. Here are some factors to consider when looking at any given commentary:
Is the commentary devotional in nature (e.g. The Daily Study Bible), or does it take a homiletic or expository approach (e.g Interpretation series)? Or is it a technical exegetical work that looks in detail at the textual, linguistic and historical context (e.g. Hermeneia series or International Critical Commentary series)? There are also academic, non-technical exegetical works that may be suitable for those who do not have training in the Bible's original languages (e.g. Abingdon Commentaries series, or the New International Commentary.) Your assignment / research needs will help determine the type of commentary that will be most useful to you.
What is the theological outlook of the author? Examine commentaries from varied theological perspectives to see the range of interpretations for any given passage. Careful reading should help you determine not only which issues are highlighted but also the evidence the authors select to support their argument.
Series vs One-volume commentaries
How extensive is the commentary? One volume commentaries can offer concise overviews, but they may not feature the fuller discussions in multi-volume series.
Who is the audience for this commentary? Is it directed towards lay readers or is it directed primarily at preachers or biblical scholars?
Is the author a scholar? If the commentary is a technical, exegetical work, does the author have the requisite expertise?
How old is the commentary? Biblical scholarship has advanced rapidly in the last thirty years. While older works may still be valuable, they will not reflect current developments in Biblical scholarship. However, consulting with older works allows researchers to see how scholars in different generations approached and understood biblical texts.
Guide to Biblical Commentaries from Oxford Biblical Studies Online
Includes online commentaries from the following sources: Oxford Bible Commentary, New Oxford Annotated Bible [NRSV] Oxford Study Bible [REB] Jewish Study Bible [TANAKH] Catholic Study Bible [NAB] Access Bible [NRSV].