I wrote about Greidanus’ method for Old Testament interpretation when I reviewed his book on Ecclesiastes.
Dane Ortlund surveys them in a post at the Gospel Coalition.
Ortlund does not mention a seventh which Greidanus uses, direct referencing by the New Testament of the Old.
1. The Way of Redemptive-Historical Progression. This interpretive strategy connects Christ to events of redemptive significance in the OT which now find their true home in Jesus–Adam’s garden testing, exodus, return from exile, and so on. Luke is perhaps the NT writer who emphasizes this the most, though it is present throughout the NT. Greidanus says this first way is “the bedrock which supports all the other ways that lead to Christ in the New Testament” (234).
2. The Way of Promise-Fulfillment. The promises of the OT, according to the NT writers, all find satisfying fulfillment only in Jesus. This includes, but is far broader than, mere one-to-one identity correspondence (Micah 5:2 speaks of a coming ruler to be born in Bethlehem; Jesus fulfills the promise of Micah 5:2). When Matt. 13:35 quotes Ps. 78:2, for example, there is seemingly no “promise” in this OT text, yet Matthew tells us that Jesus is “fulfilling” it.
3. The Way of Typology. God sovereignly acts in observable, historically-embedded patterns. For this reason the NT writers see Jesus as the final and ultimate instance (antitype) of earlier repeated patterns (types). For example, the sacrificial system anticipates a final sacrifice (cf. 1 Cor. 5:7). Hebrews is perhaps the most typologically-loaded book in the NT.
4. The Way of Analogy. By this Greidanus means the application of OT categories to describe NT realities. The main example here is the way the NT speaks of the church using language that applies to Israel in the OT. (Dispensational readers will understand the use of such language differently from Greidanus.) For example, OT Israel is called the bride of Yahweh (Jer. 2:2; Hos. 2:14-20), and this language is picked up by the NT to speak of Christ’s relationship to the church.
5. The Way of Longitudinal Themes. By “longitudinal themes” Greidanus means motifs that develop as God gradually reveals more of himself and his ways over the course of history. Big ones include covenant, God’s kingdom, law, mediation, or the presence of God. This is the strategy most closely bound up with the discipline of biblical theology.
6. The Way of Contrast. This final strategy for seeing Christ in the OT, unlike the previous five, focuses on how Christ is different from what has come before. Greidanus suggests as an example the way God called Israel out in the OT as a single nation, destroying other nations, whereas Jesus sends out his disciples to all the nations, to win them (Matt. 28:19-20).