How do you pick a middle name??

Katrina

We're team green and if it's a girl the middle name will be after my grandma, but if it's a boy my husband and I don't have anyone we would want to name him after.

Do I just pick a random cute name? I'm not a person that would ever really use the middle name aside from legal forms and what not...

I have no ideas for boy middle names, I just know that I would want it to be 2+ syllables in order to flow nicely.