"Knowing what paint a painter uses or having an understanding of where he was in the history of where he came from doesn't hurt your appreciation of the painting." -Jodie Foster
Make an effort to be polite to someone you don't get along with. Go out of your way to say hello or have a conversation with them. Getting to know and understand him or her better might help you appreciate your differences. Before you know it you might actually have a new friend!
So often we do not get along with people simply because we don't take the time to understand where they are coming from. If we knew more about them--their background, where they grew up, what they do with their free time--we would better understand why they say or do the things they do. It is always wise to be quick to withhold judgment and instead hear someone out. It is what we would want for ourselves, so we should give it to others!
Don't just wait to "run into" that person. Go up to them, seek them out, and say hello or invite them to lunch or simply start talking with them. You could even bring them a small gift! Maybe some baked goods or share a snack. Once a week go out of your way to find this person and talk with them.
Promise yourself that the next time you see this person you will be polite and smile, no matter what is going on in your heart. Ask them how their day is going, and really listen to the answer. Commit to reaching out to them every time you see them.
Read an article elaborating on why we should be nice to those we dislike.