Matched this year into so Cali program here are my thoughts on this past cycle...
Research is a must as a majority of my interviews revolved around my research and interests esp at academic places. OBviously pubs are a great plus, but I only had one manuscript submitted, no pubs, but did have 8 abstracts all presented at ddw... Start early on your research. Strong letters of rec from well known people is very helpful and can make your application stand out... The GI community is small and a lot of attendings know each other, esp GI PDs. Strong step scores def help if they are very high, esp if you have a well rounded app. Lastly, which is obvious, do great on your interview day. Be genuine, don't bs your ans as many if not all interviewers can tell if one is being disingenuous and jus saying what the interviewer wants to hear. Hope that helps, please feel free to pm with any questions.