How to limit API calls when using the Developer Console in salesforce?

You can reduce your API usage by allowing your developer console session to “idle”. Once idle, you’ll only incur one API call per incident (such as saving a class, running a test). While not idle, the current implementation polls the server once every 6 seconds, or 10 API calls per minute while doing absolutely nothing.
Also, using the Force.com IDE will drastically reduce your API calls, because you won’t suffer from the “monitoring” API calls. Believe it, it makes a big difference.