What Can I Do to Prevent Columella Scarring After Rhinoplasty?

I did one of the first open rhinoplasties in the US more than 30 years ago. Then, the criticism was making a scar in the columella. That is the easiest part of rhinoplasty. If the surgeon can't make a almost non detectable scar, he should not be doing rhinoplasties.
Choose an experienced rhinoplastic surgeon and you won't have that problem.

I assume you are talking about the inverted 'V' shaped incision on the columella which is used for approach in open rhinoplasty technique. If that is correct, you don't have to do much. Those incisions heal very well. However, an infection or suboptimal closure of the wound can lead to scarring. If you see signs of any infection, such as redness, yellow drainage, pain on touching or fever, report to your physician immediately. In terms of good closure, you should be able to tell right away if the skin incision is level or not.
After your stitches come out, use Vitamin-E to rub on it morning and night for 3 months. That will improve the scar.
Regards

People spend an extraordinary about of time worrying about scaring and healing. The focus should really be on the final results instead of micromanaging your care. Leave that up to your surgeon. They don't want you to have a bad scar either, so they are going to do everything possible to help you have the best outcome. Good luck.