[This question is related to my Dwarven Cleric character.]
In the Player's Handbook, it says that all spells need to be prepared in advance before they can be used. I get that this is done while resting but does it matter how long the rest is (i.e. long or short) as it doesn't seem to say how long each spell takes to prepare.
Also, are there any specific mechanisms for preparing spells, other than telling my DM "In this rest I will prepare X spells"?
These are both answered directly in the rules. The last paragraph under "Preparing and Casting Spells" in the Cleric class in the Basic Rules or p.58 of the PHB states:
You can change your list of prepared spells when you finish a long rest. Preparing a new list of cleric spells requires time spent in prayer and meditation: at least 1 minute per spell level for each spell on your list.
To your first question, no, you cannot change your prepared spells after a short rest.
To your second, there is a little more to it then just telling your GM which spells you're preparing as you must also spend some small amount of in-game time.
