By the high medieval period property transactions were usually conducted via charters, a legal document recording the transfer of rights or property (charters were also used in the early medieval period, but that is a bit beyond my field, someone else can probably discuss them better than I). Some areas, such as Gaelic Scotland, continued to use oral transactions of property well into the thirteenth century alongside written evidence but oral practices were eventually abandoned as charters provided stronger evidence of ownership should someone challenge the new owner's rights.

Charters normally began with a greeting clause, followed by describing the property to be transferred and to whom. The greeting clause could vary greatly, and depended on who was giving the charter. Kings and Popes had their own common styles.

After this there were extra legal clauses including terms for holding the property (i.e. paying rent), or the grantor's duties such as that described in a warandice clause. This section pledged the grantor to defend the new owner's right to their property. At the end of the charter would be sealing, dating, and witness clauses. This whole formula could vary drastically: the dating clause may be left out, particularly with earlier charters. Witnesses were not always included either.

This is a summary of a charter copied into a Hospitaller record. It details the sale of two shops in Winchester in the mid-thirteenth century:

"Sale and quitclaim with warranty by Mabel daughter of Richard the chaplain, in her great necessity, to Henry de Bello, his heirs or assigns, of two shops on St Giles' Hill in the fair of the Bishop of Winchester, between the land of William Petit and the land which belonged to William Gaie in the ancient ward of the mercers by the west of the church. To hold freely saving the service to the bishop, that is, 4 shillings annually. Consideration, 2 and a half marks paid to Mabel in her great need. Sealing clause. Witnesses: [none]."

Taken from Felicity Beard (ed.), The Knights Hospitaller in Medieval Hampshire: A Calendar of the Godsfield and Baddesley Cartulary (Winchester, 2012), pp. 43-4.

This document illustrates how a transaction fits into the feudal landholding system of the time. The donor, Mabel, has feudal responsibilites to the bishop of Winchester, namely 4 shillings. This duty is still preserved in the sale, it's just transferred to the new owner instead so that the bishop doesn't lose out.

Property development could be, and often was, limited by the terms of the charter. It was common to have a clause preventing the new tenant or owner from granting the property to religious houses or to Jews. Other charters could require the tenant to maintain the property they had acquired.

Sources: J. M. Kaye, Medieval English Conveyances (Cambridge, 2009). Cynthia Neville, Land, Law and People in Medieval Scotland (Edinburgh, 2010).