In Google webmaster tools, using your account, there is an option "Crawlspeed", but IMO it is about session crawling speed, not frequency of crawling.
Maybe that was what confused you?

For that purpose there are meta tags :
<meta name="revisit-after" content="30 days"> .
I think most engines don't accept it if you want to speed up the frequency of crawling, especially if your updates are not as frequent or much sitewide.
However I think you can use it to slow down the crawlings if you want to save on bandwidth.