1099 misc - Self employment (line 12) vs other income (line 21)

I did some consulting work on the side that was related to my primary job.  (I am a marketing professor and it was a marketing related consulting).  I received 1099 MISC from these businesses, but am not set up formally as a business.  When I enter this information it is considering it as self employment income (reported on line 12 with schedule C).  I was thinking that it would be other income on line 21.    Can you confirm what the criteria is for the line 12 income vs. line 21?  Can I enter 1099 MISC income as "other income"