First, your border does not need to go all the way around the center block. It can be on just some of the sides. Use the style of the center to guide you - a more traditional symmetrical block might work best with a more traditional all-four-sides border; an improv or asymmetrical center may not.
You can put the center on point and you can slightly encroach on the center block, especially if you are doing applique, but please respect the original design of the center. Use the color cues from the center block - if it's mostly saturated batiks, a small Civil War style floral might not work with it. You don't have to have a perfect match, but your border should complement or contrast nicely with the center.
I find the most challenging part of adding a border is balancing out the rest of the piece. If the center is very busy and detailed, the border might benefit from some free space for the eye to rest - consider adding detail to the corners and keeping the sides simple. If there are lots of triangles, maybe some squares will work well. The Cotton Robin gives us all the opportunity to try new things on a small scale.
No matter how perfectly a fabric coordinates with the center, an unpieced border (or a few strips on each side) is not enough. Your border should add to both the color and design story started by the center. Try something different - there's plenty of inspiration on the Cotton Robin blog. Look at the reveals at the end of each year to see what other quilters have done. Don't fall back on the same technique each time - if you've always wanted to do improv, now is your chance. Maybe some English paper pieced hexis are the way to go.
A helpful tip when adding a border is using a coping strip. This is a narrow strip of fabric added to one or more sides to adjust the size of the bock. If your design requires you to divide the length of the block into 4 and the block measures 7-1/2" (finished) you can add to each side so that it measures 8". A coping strip also gives a little gap between the center and border to help visually separate them.
Finally, make sure that your border is small enough to leave room for the next quilter to add a border. The maximum size should be about 20" square - if you add a 6" border all the way around an 8" block, the next quilter can't add anything to it.
Have fun, get creative, live a little!
p.s. As I've looked through the photos of the borders I've added, I see a few themes - many are on point and they are all symmetrical. Maybe this year it's time for me to try something new too.