Depends on the TLD. for .com the life cycle is as follows:-
0 Expiry
45 Registry Redemption Grace Period
75 Pending Delete
80 Registration Available*
* Any decent domain will be picked up by drop catchers within milliseconds of the drop. So it is better to backorder any decent domains at a drop catch company. Than to try to hand-register an expiring domain. The three biggest drop catchers are DropCatch ($59), SnapNames ($79), NameJet ($79). DropCatch are the most successful of these 3. But if there is more than 1 backorder on a domain, it goes to a public auction. Wheras in the case of SnapNames/NameJet, it goes to a private auction of the people who backordered the domain.