One of my favorite issues! My company builds community tools for gamers & game developers. I end up thinking about and dealing with these issues a lot.

Mobile communities are a completely new frontier. Frankly most of the technology is poor. The vast majority of mobile communities have been ported over from long standing web technologies.

In terms of moderation there has really been a paradigm shift away from handling it through volunteers or employees toward hiring professionals. Many firms have sprouted up to fill this void. You'll see publishers, marketing firms, PR firms, and agencies offering community management/moderation as part of their suite. There are also firms that exclusively handle this.

I could dig into this issue more with some more details. Community management is a giant topic that has really exploded recently.

I'll recommend lighthouse.io which is a community about communities!

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.

Adam and Gail have both provided awesome insights into this challenge you are facing. They have covered the basics I think.

Allow me to offer a whole different angle -

Starting with a 50,000 foot understanding of the landscape...

Managing communities is a rewarding and massive undertaking. And it gets more massive every year because of low barrier to entry, improved technology, and competition.

Let me tell you some of the gotchas and oddballs to consider when you decide on basics. These things are the secret under-belly of the online community - hidden things that I think will be critical to your success - stuff that only a consultant would reveal to you straightaway.

1. People love attacking, scraping, manipulating online communities. Getting hacked is easy due to automated web hackers that crawl the Internet for holes -- one hole and your whole business could be toast (if your business relies on this). And they won't just take down your site - they will upload viruses on your servers and users devices causing mass treachery.

2. Marketers love infiltrating communities
Keeping the spam out is a massive job. Marketers are crafty and do things like link switching and redirects...and they have automated posting tools too - so even if you are moderating it, they can still get in. Some communities let the spammers stay as long as the spammers are providing relevant content that blends in seamlessly...

3. Foul mouthed people - these people are easily to deal with typically with existing technologies

4. Lack of contributors - this is the biggest challenge for any online community. Out of the 100% of people that come to the community, 20% will engage, and 2% will contribute -- or something similar to that. Which means you need a 1,000 people coming to the community on a regular basis to give it life.

5. Technology - the hardest decision to make by far. There are so many different options for this. There are far too many points to discuss here -- interactivity, shareability, and simple things like registration and authentication. Which leads us to...

6. Persistent Identity - this is how you keep the spammers at bay and create powerful trusting communities. This is where you have to make another decision. Rely on other services for authentication like LinkedIn, Facebook, Twitter, etc -- or do the authentication yourself. If you do the authentication and user management yourself, you will have IP that you can sell later -- however you will need constant development to keep the riff-raff out. This is why using third party authentication is great because Facebook and Google have spent money figuring out peoples' phone numbers so that they know specifically who they are dealing with. You can leverage that.

All in all, the goal is to create a trusting and engaged community. The tools and platform are not as important as if you can get contributors involved or not. The security is important. The persistent identity is important. Getting contributors is most important. The best community platforms will be talking about these issues first and foremost. The bad tools will be painting a vision of Wizard of Oz's yellow brick road for you about how they integrate with Facebook's likes or whatever. Think your community through. If you are picking tools, pick one that has numerous prestigious testimonials. Working with beta-type community platforms is a no-no.

Most communities seed the content much more than your average consumer would think. Reviews are seeded, stories, posts, photos...it's kind of like a retail store that has no one inside shopping -- if window shoppers look in and see that no people are inside, they will keep walking... Imagine your friend egging you on saying "oh oh, you need to go viral, you need to go viral"...well you do, but viral campaigns are usually started by pushing the snowball all by yourself until it grows big enough to roll on its own...

Seems like you may need some help with creating a custom plan -