Federal Register & Comment Periods
The Federal Register is the official journal of the government of the United States. Many agencies publish their grant notices in the Federal Register. You can search the doucment on the website or you can subscribe to receive either the entire document (not recommended due to its size) or the Table of Contents (recommended) daily via e-mail.
As well, many grant notices have comment periods where the public can provide feedback on them before the competition officially begins. As comments periods precede the grant application period, seeing a grant go up for comments is a singal that the grant application period will soon follow. Therefore, by starting to work on a proposal during a comment period, you have a longer window within which to prepare your grant.