It is worth noting that the save functionality in Kingdom Come: Deliverance is not like that of most games. Not only is the player limited to a specific number of saves (currently capped at 24 without mods), it is only possible to save at specific times and in specific places. The two regular methods of saving are the following:
Sleep and Save
Allows the player to use a bed to save the game, though not all beds can be used for this purpose. Those viable are usually associated with residences where Henry is recognised, such as the Rattay Mill shown below.
The Saviour Schnapps potion allows the player to save the game anywhere in the world, excluding only when Henry is in combat. Although this method means that the player is not obliged to find viable beds to Sleep and Save, it has the unfortunate side effect of contributing to the development of alcoholism, which is detrimental to Henry's stats. In addition the potions are relatively expensive early in the game and are not stocked in high quantities by vendors. Alternatively they can be found throughout the map in hidden locations, most frequently in caches located in and around bandit camps.
Note: If you are having difficulties finding appropriate beds to Sleep and Save and having trouble balancing the retention of memories with excessive schnapps consumption, there is one final, somewhat tiresome option; press escape and choose to 'Save and Quit'. This will close the game but allow you to return to the point where you left off if you had to quit in a hurry. However, keep in mind that the save will be deleted once you reload it, so you will have to resort back to sleeping, drinking or breaking immersion with another Save and Quit.