API designing - best practice and how to support multiple versions

What is the best way to design the API's which supports multiple versions. How do I ensure that even if the schema of my data changes(minor changes), the consumers of my api's are not affected? Any reference architecture, guidelines is really helpful.

How do I keep multiple versions of API?

For simple APIs you can maintain different versions by defining a Constant in your app. This constant will be the path to the root of your API endpoint. Typically this would carry the same name as your app's version, like "myApp/v1-8-5/" assuming your app version was 1.8.

Mark Nottingham has a good blog post on how to version Web (REST) APIs

http://www.mnot.net/blog/2011/10/25/web_api_versioning_smackdown

Also about API versioning in general:

http://theamiableapi.com/2011/10/18/api-design-best-practice-plan-for-evolution/