If you have never tried the expository approach to preaching and teaching before, but want to try it, numbered here are some ways you can do it poorly. When constructing and delivering an expository message that will fail to actually be an expository message:
1. Make the Scripture fit your agenda.
If you must contort the message of a Scripture, or if you feel that you must take intellectual leaps with the Scripture to make it flow with your preconceived thesis, then you are constructing something other than an expository message. The strength of an expository message is in the Scripture itself. You are merely delivering what the Bible says; not trying to make the Bible say what you had in mind to say before preparing your message. You are the messenger; not the Author. There is comfort in that, but there can be wariness too. The comfort comes in the fact that convicting and difficult aspects of your message came straight from the Holy Spirit and not from you. This takes pressure off of you. The wariness comes in the fact that you must teach difficult passages. Do not feel as though you must heavily massage every difficult passage in your teaching so as to avoid making un-churched visitors uncomfortable. In my experience, skeptical guests very much appreciate having their tough questions on tough passages answered by clear and substantiated historical-cultural context.
2. Show no regard for the original intent of the Scripture.
This is another way you can fail at expository teaching. If you provide an insight with which the Spirit-inspired original earthly author would disagree, then you have not only failed in that moment at expository teaching, but at Bible teaching in general. There are multiple forms of context and an expository message contains elements of some or all of them in various proportions depending on the passage. However, a message that pays no mind whatsoever to literary context, historical context, cultural context, or theological context is not an expository message.
3. Instead of giving a Spirit-filled call to obey the Scripture, just give a rich lecture.
If you do the work of exegesis (digging into the original context), but do not do the work of hermeneutics (showing people how the original context relates to them today), then you have merely given an historical lecture or textual analysis. By all means, do the work of researching the lives of the original recipients. Understand the political climate of the biblical day and know its seemingly odd cultural idiosyncrasies such as the trading of sandals to seal a deal at the city gate. Research the context deeply, but do so with the understanding that much of your work in exegesis will not be a part of your message. Rather, research the original context, share what is necessary in the message, and leave the rest on your messy desk knowing that it has ensured theological accuracy in your teaching.
We are not called merely to educate. We must be filled with the Spirit. We do not explore a dead document. The Word is living and active. So, call people to action in light of what Scripture teaches. Much of this depends on your time management. Too often, a leader enthusiastically educates his group; sharing with them fascinating insights into the biblical world, but runs out of time and says nothing of what Scripture has to do with today. Oh, the pain of the wounded man who seeks answers from group Bible study or preaching, but goes home having been given only historical factoids and a parsing of a Greek verb. Think on the question “Now what?” throughout your session or message. Prioritize time for showing how the Scripture applies today. Because you have done the work of exegesis and because you have shared pertinent aspects of that research in your teaching, you can call people to live out Scripture in a way that is consistent with Scripture’s original intent. Then watch the Holy Spirit take the Word and radically change lives.