Clarify where to ask questions

CONTRIBUTING.md

@@ -2,6 +2,18 @@
 
 Thanks for your interest in contributing to OpenLayers 3.
 
+## Asking Questions
+
+Please ask questions about using the library on [stackoverflow using the tag 'openlayers-3'](http://stackoverflow.com/questions/tagged/openlayers-3).
+
+When you want to get involved and discuss new features or changes, please use [the mailing list](https://groups.google.com/forum/#!forum/ol3-dev).
+
+
+## Submitting Bug Reports
+
+Please use the [GitHub issue tracker](https://github.com/openlayers/ol3/issues). Before creating a new issue, do a quick search to see if the problem has been reported already.
+
+
 ## Contributing Code
 
 Our preferred means of receiving contributions is through [pull requests](https://help.github.com/articles/using-pull-requests). Make sure
@@ -25,7 +37,7 @@ You will obviously start by
 
 ### Travis CI
 
-The Travis CI hook is enabled on the Github repository. This means every pull request 
+The Travis CI hook is enabled on the Github repository. This means every pull request
 is run through a full test suite to ensure it compiles and passes the tests. Failing
 pull requests will not be merged.
 
@@ -78,7 +90,7 @@ The `build.py` script is equivalent to a Makefile. It is actually based on
 The usage of the script is:
 
     $ ./build.py <target>
-    
+
 where `<target>` is the name of the build target you want to execute. For
 example: