It's competitive, but not overtly so like the surgical subs. 230/550 is kind of the magic line to be at score wise where your chances of matching increase significantly, although people match with scores below that every year. The general rule of thumb is 230+ is good, 240+ is better, and 250+ is icing on the cake and will open some doors. Obviously not a hard and fast rule. I personally know people in the 220's who matched solid programs this year. You absolutely want to take Step, not having it will limit you severely in where you can apply (I.e. only former DO programs pretty much). There are even former DO programs now that are requiring Step of all applicants, ex. Swedish in Denver.
Research is always a plus. If you are targeting MD programs then it's a must. Actual peer reviewed publications are best but most DO students have case reports, posters, etc and that is ok too.
Class rank is always nice to have but won't be what ruins any applicant.
Here are some things that I've seen help DO students and will help set you apart from other DO applicants. 1. LOR's. Most MD GS applicants have 3 letters of req from general surgeons. A lot of DO applicants will only have 1-2 and then have non-surgeon letters. Having 3 surgeon letters, with one being from a PD or Chair will go a long way. 2. Aways. Obviously for DO programs the audition is still a big deal, but even for MD programs an away can be what gets you in the door to a place that might not have given you a chance without being able to see you I person. They also serve as a great way to get letters of req from academic surgeons (a lot of DO surgeon letters are from community PP guys that precept students).
Since you go to a state school you will likely be at a clinical site with a residency. Make connections, see if the residents need any help with research projects, if it's the culture of the program to let students show up to didactics then pop in from time to time as your schedule allows. Get to know the interns as they are the closest to where you currently are and in my experience are generally willing to give advice and help you. Be around but don't be annoying.
tldr. 230/550 is the threshold where matching chances go up quite a bit, have some research, get 3 LOR's from surgeons, be a cool person that isn't annoying. Good luck, General Surgery is an awesome field.