You must be logged in and on the search results screen before you can place a hold. Click on the checkbox next to the item: Click on Place Book on Hold:
You must be logged in before you can place a hold. Click on Your Account: Clicks on Holds:
You must be logged in before you can place a hold. Click on Your Account: Clicks on Holds:
To check out a held item that is now available: Click on Your Account: Click on Holds:
You can have up to 10 active holds.
Holds are set to expire six months after a request is made. If the item is not available to checkout by this date, the hold will expire. 
The amount of holds ahead of you before your item becomes available to checkout.