How to take over expired domain name?

If the domain gets expired then you can take that domain just like you take new domain but if the original regsitrar still maintains the webpage then you may have to purchase the domain from the original registrar by paying some more money then normally to be paid

theres some services available which will try and grab the name first for ya when it expires, actually i think its 90 days after it expires it goes to the free pool

Do you really want to do that?