How do you handle Declarations in your FATE games? Specifically:
Are they always Perception or Knowledge-based (i.e., are you generally using Search/Investigate/Alrtness and Scholarship/Knowledge)?
Or are you and your players using other skills to create them, when justifiable?
They're based on knowledge, perception, and pre-existing fact yes...but not Knowledge and Perception skills alone. Declaring you own something may be Resources, declaring a custom pistol round is probably Firearms, declaring you've practiced picking a lock type before is Burglary, etc. Scenery declarations will often use the Perception skills and "I know X" declarations will use Knowledge skills but they're a subset of the whole.
Do you handle them as a free action (as the rules indicate)?
Or do you consider them a different kind of Maneuver that still takes an action (or supplemental action), with the rationale that the character is spending an action to "notice" the element which they are Declaring?
Would you be inclined to make them free Actions if the player did not get a free tag?
They're a free action, after all they're pre-existing. If they're changing something or acquiring something they didn't have before it's probably a maneuver. But Declarations are generally past tense or statements of being.
Do you find your table has a natural "saturation point" on Declaration-based Aspects?
Or do you find a way limit them?
Are you and your players spending every action making them, because hey: free Aspects?
I set soft limits* of one per skill per scene...and still don't get as many as I'd like to see in game.
*By 'soft limits' I mean the target number for success goes up on repetitive declarations.