Question: How to optimize for image search

One of my sites get a fair percentage of organic from Google Image searches.
I'd like to be able to investigate further which keywords people are using to search for images.

Does anyone know of a keyword research tool for image based searches?

Thanks in advance.

 

Using the right key, such as:

Using ALT attributes smartly.

<img src="file URL" alt="file description" />

Code (markup):

Naming follow the file's content
Ex: Image file: vavietnam.com/images/quang-ba-website/20-mat-phap-quang-ba-trang-web-cua-ban.jpg for the page 20 mật pháp quảng bá trang web của bạn (Content in Vietnamese)

v.v..

 

The most importantly thing is to enable enhanced image search in google sitemasters tools