How to identify which keywords is giving more conversions?

I am running a customer support campaign. Here conversions are to tends to no. of calls.
customers visit our site and pick up the number and give us a call. In this case how I can check which keyword is giving more conversions?
If you have more clicks that doesn't means you have large number of conversion. May be that particular keyword leads to be generating less number of conversions but getting more clicks /traffic

So how can I check which keywords have higher potential for my campaign?

In this case we cannot track keywords because he conversion is upto the customer if he/she want to call or leave. So is there any way to check conversions ?

You need to use tracking platform/tool like prosper202 , clickmeter ...etc

use the conversion pixel - its easy to implement and you will see the conversions in adwords

Are you able to link Analytics with AdWords? You can add event tracking on buttons so you know which actions were taken.

First of all thanks for all your replies
But there is no button Customer see the number and make a call.
Anyone can track button clicks for mobile devices but how you set conversion for computers.
I think no one click any button to make call while using computer. He/she just pick the number from the website and dial with their mobile phones.

Is there any way to track this kind of conversion?

You need to go one step at a time, don't try to optimize both ads and keywords at the same time.

First, you need to cut out non performing keywords with low CTR. They are anyways expensive and will yield a poor return.

The next step is to test different ad copy (I suppose you are using Search and not display) and keep the one performs best.

The goal is to get calls You need to track your overall conversion rate rather than which ad gave you calls.

Hmm.... After doing a little of research by simply asking big G, it looks like that it is possible to do. Basically, you will get different phone extension for each keyword ro something similar. I didn't go indepth, so you might have a look. https://support.google.com/adwords/answer/6095882?hl=en