What would the ceremony for a king confirming the land and title of a vassal consist of? I assume their would be some kind of formal script like the vassal kneeling and pledging loyalty in front of the throne followed by a feast.

Well, here’s how it worked in Medieval Europe. From Wikipedia by way of Anne Duggan’s Nobles and Nobility in Medieval Europe:

“The would-be vassal appeared bareheaded and weaponless as a sign of his submission to the will of the lord and knelt before him. The vassal would clasp his hands before him in the ultimate sign of submission, the typical Christian prayer pose, and would stretch his clasped hands outward to his lord. The lord in turn grasped the vassal’s hands between his own, showing he was the superior in the relationship, a symbolic act known variously as the immixtio manuum (Latin), Handgang (German), or håndgang (Norwegian).[1] The vassal would announce he wished to become “the man”, and the lord would announce his acceptance. 

Now there were variations on this model: often there was an exchange of tokens, such as rings, to signify mutual aid and fidelity; when a king was confirming a religious office, he handed the new bishop or whoever a crook staff (although this was a major source of disputes between church and state); sometimes, the ceremony of homage would be combined with the knighting ceremony so that there would be a dubbing; etc. 

But the basics of a symbolic show of submission and trust on the one hand and protection and honor on the other were usually the same.