You can study this for yourself by downloading the Splunk Dashboard Examples app, the Web Intelligence app (and others). Study them while reading the manuals: Developing Views and Apps for Splunk Web and the Splunk Data Visualizations Manual.
The Sideview Utils app is a very popular tool for Splunk app developers. You should certainly consider it, as it provides a lot of enhanced capabilities. It also can be downloaded from Splunkbase. Read the license carefully if you want to distribute your app.
In addition, I think you would find it very worthwhile to take the class: Developing Apps with Splunk
There are prerequisites, but you can find out more at the link. [Disclaimer - I work at Splunk as an Instructor. But I hope that others would agree that the class is worthwhile.]
You might also want to check out the free videos to learn more about Splunk: http://www.splunk.com/videos
Finally, if you want to actually write code that uses a Splunk SDK or the API, check out http://dev.splunk.com/, which has a number of resources for developers.
