If a “phase” of a turn provides no player agency and cannot be affected by another player, try putting that phase at the end of the turn. Examples of this are drawing cards, collecting resources, cleaning up markers, etc. This can sometimes result in several of four slight improvements to your game.
Players may have an easier time planning out their next turn as performing rudimentary admin as soon as possible gives each player their starting setup for their next turn earlier, allowing players to more easily plan out their strategy ahead of time. This is most apparent with drawing cards. In Dominion, (and, by adoption, most deck builders), players draw a new hand at the end of their turn, allowing them to plan out their next turn during what would normally be considered down time. This effect works with more than just cards, however. Say each turn involves collecting 2 gold. If I collect 2 gold at the start of my turn, after every other player has completed their turns, then any plans that I make between turns has to include the thought “I’ll have 2 more gold on my turn.” Collecting resources at the end of a turn allows the player to reason about their next turn with the proper resources in their supply.
Putting admin at the end of turns creates opportunities for you, as a designer, to add more player interaction to the game, as players will immediately collect the resources that their opponents can affect. In Dominion, for example, opponents can force you to discard cards, giving you fewer cards on your next turn. If you only replaced your hand at the start of your turn, this wouldn’t be possible. In general, setting up for the next turn early allows other players the opportunity to affect that next turn.
Putting admin at the end of turns allows the setup instructions to more easily affect the player’s first turns and may reduce player confusion. Say you want players to have 5 cards at the start of the game, but they draw 2 cards at the start of every turn. Do you start them off with 3, or start them off with 5 and skip the draw on the first turn? If you start with 3, the players may get a little confused. “So, I start with three but I immediately draw two more?” If you skip the draw on the first turn, you’re adding extra rules that players have to remember for only one turn. If the admin is at the end of the turn, you have none of these problems, the setup is the sole provider of resources for a players first turn, and the end-of-turn admin phases handle every turn thereafter.
Finally, putting admin at the end of the turn allows experienced players to start performing their turn while the previous player is finalizing their turn, reducing downtime. In Dominion, I often have to shuffle my deck in order to draw my next hand, but any player with even a few games of Dominion under their belt knows that they can start taking their turns while I’m shuffling. Of course, there are card effects that can only be completed once I’ve drawn my hand, like the Military, which forces me to discard cards, but experienced players will simply wait to play the Military card until after I’ve shuffled and drawn, or they will go ahead and play the card but just inform me I need to discard once my hand is drawn.
In theory, you could overlap turns with admin at the start of a turn. A player could start collecting resources and cards while the previous player is still finalizing their turns, but it’s harder to know when you can start that process. If I start collecting resources and an opponent performs an action that causes my resource count to be relevant, I would need to remove the prematurely collected resource before my opponents action can take effect, which may be cumbersome. With admin at the end of turns, the player who is choosing to go ahead and perform their actions is also, presumably, the player who knows if those actions need to wait for their opponent to actually finish their turns.
There are reasons to put admin at the start of the turn, and if you have one, feel free to do so. Quite often, however, putting admin at the end of turns results in less downtime, more player interaction, and easier setup.