I don't know the "soft spots" in DL's pricing, so can't offer a lot of specific advice.
My best advice to you is to look at cities served by Southwest Airlines - they tend to drive down prices in a market. You can go to their website and see the cities they serve.
For example, in Hartford I can do BWI for $99 RT. 4 segments/2000 miles. Not a ton, but terrific for topping off Elite status.
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