I clipped a piece of my friends basil plant - how can I replant it and make it grow?

u must first cut the stem on a 45 degree angle, scrape the
side of the stalk 1 inch up to the bottom with a razor blade
dip the stem in some rooting hormone {Take Root} is the
name. Then put the stem 1 and a half inches into a heavilly
moistened cup of good dirt. Will root in 5 to 8 days .
{Take Root} is sold at all lawn
& garden stores.

Basil roots in water.

Just stick it into a pot of soil, keep the soil moist, and give it some nice bright light. It should root in no time, and you'll have your own basil plant :-)

If that doesn't work, they're easy to grow from seed, too.

You have to "root" it first. It is a easy thing to do. Just put it into a glass of water and place it in window that gets good sunlight. By the time Spring rolls around, it will be ready to plant.