Best way to clean coolant out of carpet?

I would start with some Dawn detergent, water, and a scrub brush. Scrub it, and dry it with a towel. A shop vac would also help. Rinse, repeat. Then go after it with some carpet cleaner available at Wal-Mart, O'Reilly, Autozone, etc. Follow the label for instructions.
Also might want to pull the carpet back for awhile, and let the padding dry up if necessary.

PS: Or get some new carpet. Looked it up, and its only $150 for a fresh carpet kit. :)