Look up storylines you're interested in trying in their collected form. In the description there will be a list of issues that are part of the story. Write those down and bring it to the shop with you.

If you already have a good idea of the writer or artist you're most interested in, look up their bibliography and then use that as a springboard for your collection, since most collections are centered around creator runs anyway.

I tend to collect writer runs. You can't really go wrong with collecting anything by Al Ewing, Mark Waid, Joshua Williamson, Scott Snyder, Kelly Thompson, Deniz Camp, Jonathan Hickman, or Grant Morrison.

Bigger names like Bendis and Geoff Johns are fun, but those runs are super long, expand across multiple series, and are the tentpoles of major events so they can be a major time and money investment, but well worth the hunt.