we installed some third party managed and unmanaged packages in dev sandbox. we need to move from sandbox to production. what is the recommended way to migrate managed and unmanaged packages from sandbox to production.
Don't use packages for migrating changes from sandbox to production!
Managed packages are for publishing commercial applications. They are upgradeable, but they can only be created from a Developer Edition organization, not from a Sandbox. so you need to install that separately on your PROD again.
Unmanaged packages are NOT upgradeable. Once you install a component into your production organization using a package, you can change it in your organization but you cannot install another unmanaged package with a newer version of that component into your production organization (unless you uninstall the original package, deleting any data in its schema in the process).
Instead, use the Deploy to Server wizard in Force.com IDE (for Eclipse), or write a script for the Force.com Migration Tool (for Ant), You can also opt changeset to migrate the changes.
Here's a great post on deployment best practices in the Force.com IDE: http://wiki.developerforce.com/index.php/Deploy_Force.com_Applications_Faster (link)