-Be coherent with your skill level: For example, if your character's tailoring skill is 'mediocre' it makes little sense to craft 'an alluring masterpiece that draws the attention of everyone in the room'.
-Don't abuse descriptions: Similarly, stating that a piece of clothing 'entices your imagination' or something that involves another player's actions or feelings is inappropiate and considered powergaming.
-Respect materials: cotton is cotton, not white gold. Stick to the material you're using. It's ok to add beads or rhinestones for instance, but not to make a gold pendant out of a bolt of leather.
-Respect intentions: Tailoring is for making clothes, not props. Don't make musical instruments, baby alligators, severed human limbs, weapons, vehicles, just don't make props with material.
-Brevity: try to keep your messages on the brief side. Making a text wall for a single item worn discourages players from reading your char's descriptions or even looking at them.
-Be original: doing a replica of an item already sold in stores is bad. Don't make plain silk dress shirts, simple sneakers, or microdresses, those already exist in game.
-Don't cheat: making items that try to pass as hoodies, ponchos, shrouds, umbrellas, or specially armor is not cool. Don't try to make anything that can confuse a player -- tailored items can't be codedly used as disguises or armor.
Furthermore, it's possible to simply fail at tailoring. Inadequately-skilled people who get their hands on some material might find that they can't make it into what they want to make it into, or, can't finish it once they get started. Beyond this coded hurdle, adhere to the guidelines above.