Tam, Coleus are easy and fast rooting. Cut 3 1/2-4" stems, remove bottom leaves. Some people remove all but the top two leaves. Set stems in water, (toss old water, add fresh daily.) They should start rooting 7-14 days.
Place in medium light, no direct sun.
After roots are about 3-4", pot in soil.
Since you don't want to throw anything away, keep the trunk, too. After taking cuttings, grow the trunk as you would a fully mature plant. It'll send out new stems and foliage, might even grow fuller, thicker/larger leaves.

Do you pinch? The secret to growing Coleus successfully is to pinch stems every couple months..It's said to remove flowers, since they're insignificant, take nutrients that'd should be directed to foliage.

Coleus can live for years, but after the 4th or 5th year, it's best to take cuttings and start over. When they're older, they grow spindly, which is where pinching stems back, helps. Toni

It depends on the vitality level of the plant and the cultural conditions to which you subject it after the chop. A plant that is growing robustly should back-bud from a stem chopped as short as 1/4" above the root flare.

Al

I dont pinch until i think the plant is tall enough.It's only about a foot tall.

I still haven't figured though,is it better to root in soil or in water?

Chris is my real name,by the way.

It's better to root in a sterile, well-aerated medium like perlite, very coarse sand/fine gravel (1/2 BB-size to BB-size), screened Turface, or screened NAPA floor-dry, than it is to root in water - even if rooting in water SEEMS easier.

Al

Hi Chris. I'm not telling you what to do, but after growing Coleus for years I find it best pinching side growth. If you want your Coleus to grow tall and upright, then, like raising an Avocado, it's better to wait until your Coleus gets 'x' high, then pinch. But side shoots are better off pinched so they don't grow spindly, especially in winter.
Your Coleus is 1' tall? Is your goal to grow tree-like? If that's the case I'd love to see the outcome. Home Depot is selling Coleus trees this year. Something I'd never seen before..They're quite interesting, but expensive,...49.99! lol
What color is your Coleus? Do you know how tall the type you have gets?
I bought 5 different Coleus and planted on the side of my house. I planted from tall to small..the smallest in height is 8-10". Well, that's what the tag reads.
Those at HD are about 4' tall. I wish I knew which Coleus they are..it's more economical and pleasurable making your own. Do you have a picture, of if not, what's its color? Toni

Well,I had changed my mind about cutting off the top,but my friend accidentally knocked it with a bad while helping me bring in groceries,so I guess i have to start from scratch.

It has deep red foliage with yellow-green edges.If i recall right it can grow to about three feet.

I might just go buy a new one since they had at least 40 of that variety out there.So i'll plop the knocked off top in some water and wait for roots.