This page covers the aspects involved in creating high-quality animated GIFs to demonstrate certain Terraria animations, including a step-by-step workflow guide.
See below for two free programs for Windows and Mac OS X for creating screen-recorded animated GIFs.
The only objects visible within the arena should be its floor, standard Torches if necessary, WoodPlatforms, if needed, and, for demonstrations of weapons, Target Dummies (in addition to anything else necessary for the demonstration).
Ideally, utilize only the daylight. If that is not possible, place only as many standard Torches as necessary for every entity to be seen clearly. Too many Torches without benefit for the lighting only act as a distraction. Preferably, every part of the arena has the same light level.
5)
Use the default male character.
Use the default character settings.
Remove/hide all accessories and dyes that are not necessary for the demonstration.
Unless they are part of the demonstration, deactivate all pets, light pets and minions.
Unless armor is being demonstrated, remove or hide all armor with the Familiar set (effect-causing armor, such as Beetle armor, should be removed).
6)
Record the aspects of the item you want to demonstrate.
Make sure the mouse cursor is not visible unless part of the demonstration (e.g. Xenopopper). The standard red mouse cursor is preferred, in case you decide to include it.
Furthermore, make sure there are no unnecessary UI parts of the game (such as the edge of an opened inventory or health/mana bars) visible in your recording area.
Focus on the core aspects you determined in step 2). Demonstrate each one of those not more than three times.
7)
Edit the video recording.
Crop the video to a size as small as possible, making everything that does not belong in it disappear. You should leave a certain margin around the area of the demonstration, though, so that the GIF is still pleasing to watch.
Cut the video to only show the necessary part. Do not extend the GIF with unnecessary repetitions of the same animation already shown! Every additional frame increases the page's loading time.
8)
Export/save the GIF.
Example[]
This is a workflow example for creating a GIF demonstrating the 光束劍.
Step
Applied to Example
1)
Read the Terraria Wiki article of the item you want to demonstrate carefully.
Determine the aspects you want to demonstrate, based on the wiki article's information.
The sword shooting a projectile when swung.
The projectile dissipating upon hitting an enemy.
The cooldown of the sword projectile, i.e. the sword not firing a beam on every swing.
3)
Determine what is required to demonstrate those aspects.
A Target Dummy to shoot the projectile against to demonstrate the incapabilities of piercing of the projectile.
No other distracting particles or items are necessary to demonstrate the determined aspects.
4)
Build a clean arena where you can demonstrate your item.
Do not worry about the outside of the arena. You can crop it after recording.
5)
Use the default male character.
Use the default character settings.
Remove or hide all equipped items.
6)
Record the aspects of the item you want to demonstrate.
Put the Beam Sword in the hotbar and close the inventory to ensure there are no UI elements included unintentionally.
Swing the sword one time, demonstrating the sword projectile.
Swing it another time immediately afterwards to demonstrate the cooldown and the projectile not firing upon every swing.
Swing it a third time after the cooldown has elapsed to demonstrate the projectile firing again.
7)
Edit the video recording.
Crop the video to only include the area of the character and the Target Dummy. Leave a small margin around them and make sure that the damage numbers are not cut off, so that the GIF is still pleasing to watch.
In case you have swung the sword many times, cut the video to only include the three necessary swings.
Both programs are free to download and use. Using ScreenToGif is recommended because you can quickly record everything you need, crop, cut and export from the same program.
Windows and 
Mac OS X for creating screen-recorded animated GIFs.
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光束劍.