There are numerous variations, depending on intended application and personal preference. From a basic jump-stop guide to full chain retention with bashguard. If you wish an education, peruse the illustrious 1x9 thread (link).
The easiest/least expensive is probably what I did: BBG bashguard on the outside and N-Gear Jump Stop on the inside, remove front derailleur and small chainring and you're good to go with no chain drops. Total cost: less than $30 including shipping I ran without the bash and jump stop for a couple of ride but dropped the chain in rough stuff quite often, just depends which gear you're on at the time.huevos said:A 1x9 seems like a pretty straight forward project, and there have been quite a few questions about the nuances of such a drive train, but I havent been able to find a thread which explains the parts necessary in a succinct manner...so...go at it. Explain the parts necessary for a 1x9.