Given the time it takes to moderate communities well, finding volunteers to do that for free is not likely. It is better to hire a community manager who already has experience who is willing to keep growing as communities change.

Reddit is a perfect example of a community that businesses would probably want to avoid. Why is explained in http://www.dirjournal.com/articles/reddit-guide-how-to-use-reddit/

Each community is different and requires different skills, tools, and strategies. Here are some you may find beneficial:

These posts explain the currently available tools for managing Instagram communities http://www.socialmediaexaminer.com/instagram-community/
http://www.ignitesocialmedia.com/community-management/instagram-direct-means-community-managers/
http://www.razorsocial.com/instagram-tools-to-grow-your-presence/

Tips for using Snapchat
http://socialmediatoday.com/amy-birch/1402306/how-use-snapchat-part-your-marketing-strategy

Strategies for Vine
http://blog.360i.com/360i-news/5-best-practices-for-brands-using-vine

There is a Google Plus Community Manager group where you can find discussions and strategies: https://plus.google.com/communities/101510889779807726729

You can find many more tips online such as Mashable's 12 Top Community Managers Share Their Tips for Better Engagement http://mashable.com/2012/03/15/community-manager-engagement-tips/

I hope these cover what you really wanted to know. We would need more specifics (platform, business, goals) to answer more clearly.