I was a successful second time applicant also.
This time, I applied only to my in-state contract schools and two oos schools (one I applied to last cycle, one new). I just took the advice given by the different admissions' offices at the end of last cycle; I increased my GRE to over 300, I got more human volunteer hours, continued getting more hands-on vet experience hours, and had 3 letters of recommendation by veterinarians VS the 1 I had last cycle.
Honestly, one of the downfalls I was told was that I went to a small, liberal arts college and those are typically perceived as "easier" courses. I branched out and took a summer course online with Purdue University since it's a more well-known school. Not sure if that actually had anything to do with my acceptance this year, but I feel it didn't hurt (and I needed that course for two schools I applied to anyway xD)
If grades are your main worry, pick up some summer courses or online courses, if you're able to.
If you didn't have many human/community volunteer hours like at a nursing home, shelters, town functions, etc, definitely pick up some to add ot your application. Last cycle, I honestly did not think it was a huge deal to put that on my application but one school was really looking for those community service activities and that's the school that I got accepted into this cycle; so I think it definitely made a difference. 🙂