Photograph the clothes on a hanger or mannequin if you have one - not on the floor and against a plain background.
Photograph all angles
Include a picture of labels and material.
Include measurements
If you are selling bags list what it is made of and the length of the strap - especially across body bags.
Be honest about the condition of the item, insuring you list any faults
Price to sell with a small margin to accept offers
Offer a bundle discount - vinted automatically set it to 50% so if you don't want to offer that make sure you change it.
Offer as many courier options as you can as not all couriers are available in every area, some you need to print labels but most you print at the shop when dropping off.
Royal mail you need to pay up front but get the postage back when the transaction completes - buy the postage online and the postman can bring the label and collect for free at the moment, but as it is not an integrated service it does not automatically complete the transaction 48hours after delivery like the others do.
Once the transaction is complete leave feedback for your buyer - sellers get automatic feedback if the buyer does not leave any - the buyer does not get any unless the seller leaves them some.
There is a whole section in the vinted help centre on selling which would be worth a read.
Read up on how they expect items to be sent because if they are damaged in transit the buyer will most likely get a refund and the seller gets nothing if vinted feel they have not followed their T&Cs. They suggest items are sent in a box.
Good luck @AppolloandDaphne