I've never made a resolution, but this year I did. I have committed to running 500 miles this year. I started trail running last year around April and loved it. I averaged approximately 6 miles a week and only ran until October.
With this commitment (which I will track with a group friends), I have to run an average of nearly 10 miles a week for 52 weeks. During the winter, it will be on the treadmill, and when the snow melts and it warms up a bit, I'll be heading outside for my trail runs.
I also plan to start Yoga this year, but that's not in my resolution.