I have not sewn one, but have heard great things about this pattern: http://sewliberated.com/products/mei-tai-baby-carrier-sewing-pattern
(She also has a great blog, and is a fellow Montessorian - small world!)
Mama to DD born 1/28/12, and baby #2 on the way in January '14!
This is the pattern I use. http://www.sleepingbaby.net/jan/Baby/man-tai.shtml I love it because it has pictures & very detailed, step by step instructions. Regular sewing instructions confuse the heck out of me. I've made several really great MT's using this pattern (although I don't put the pocket in mine).
mom to all boys B: 08/01, C: 07/05 , N: 03/09 , M: 01/12 and far too many lost ones