When a visitor clicks on the Ads or view Ads, publisher (website owner) is credited somewhere in between 0.01$ - 10$. A publisher will be paid in last of the next month when he completed his earning 100$ or more. That means if you have completed earning 100$ in January your check will be sent at your given address at the end of February.
If any one failed to complete earning 100$ in a month nothing to worry, it will be carried over to next month. That is if you earn 40$ in January and 60$ in February then your check will be sent at the end of March. Receiving check in US $ is open for all country. In some countries they also offer check in local currency, EFT (Electronic Fund Transfer) and Western Money Transfer. In India Google offers check in Rupees. If you want to increase AdSense earnings, firstly you should increase your site traffic. After the optimization of site traffic you are applying the first Ad unit rule.
Do you know about the importance of first Ad unit in AdSense Ads? The first Ad unit shows the most paying Ads for your site. First Ad unit means which Ad unit you have placed first in your site html code. By using channels you can easily track which Ad unit is getting maximum number of clicks. If that Ad unit which you have entered first has maximum CTR (click through rate), you need not to change it. But if other Ad unit gets maximum CTR, then remove all the Ad code. Then enter the code for that Ad unit first in your site's code. That will help you to earn a lot more than to usual.
Read here to know the primary tasks to earn through AdSense
