A.Domains that expire at Dinsol.net are released after their term expires. Please remember when looking at a domain's expiration date that the format is Month/Day/Year- MM/DD/YEAR.
Domains that expire at another registrar are subject to their own policies. They do vary from registrar to registrar, however, there are some consistencies.
There is usually a grace period, and then a period when the domain is "on hold"- where nobody can do anything with it.
Generally, you will need to give a domain at least 30 days from the time of expiration to be released. You cannot put in any kind of "pre-claim" on the name. You'll have to wait until it is released by the registrar, and then register it manually. Lately, Network Solutions has adopted the policy of not releasing domain names. If a name expires at Network Solutions, they will require it to be re-registered at NSI.
For a registrar's specific release policy, you should contact the registrar that owns the name. You can find out who is the registrar for a specific name by entering the name into the central database search engine at http://www.internic.net/whois.html.