The key to selling any NFT (item) is two fold:
Have good content on the NFT, such as high quality artwork, or a valuable domain
Be descriptive and give the buyer a reason to buy your item
If you have a low resolution gif from a random website - most people won't buy it. There isn't a reason, especially if you didn't create it yourself.
Successful NFTs sold all have one thing in common:
High quality content
A high resolution, custom made, beautiful artwork is much more likely to sell, than a random photo of your dinner.
Making something rare means there will only be X amount of them ever made. This means there is a resellable factor. A buyer can purchase the item so that they can resell it for profit. Making you and the buyer both crypto.
Rarity also increases the collectibility factor - where someone will want to buy and hodl onto that item because its rare and there are only so many.
Giving the buyer something special to access once they buy the item is vital to being a successful seller.
If you are selling artwork and the image everyone can see and copy and paste is the same image that the buyer gets to download, there isn't much incentive for them to download/buy that item.
But if you have a watermarked, lower resolution version as the public image, and only the buyer can download the 4k high resolution non-watermarked copy - they are highly incentivized to buy it.
You can give them a .zip file to download with multiple files as well.
Make your item collectible. Give it a reason to be collected and resold or held onto.
If you own a website - use the NFT as a coupon on your store, or access to special part of your forums.
Make the item apart of a collectible series, or make it so that collecting 5 of the items grants the buyer something special such as some merch from your brand.
Make sure whatever you make it is beautiful or high quality. Even if your selling a domain name, a beautiful image or video explaining why that domain name is so valuable increases your chances of selling your item by a lot!
Write a good description, include a video or images to explain why your item is valuable. If you just put one or two words for your item, it probably won't sell
This description has a youtube video, detailed message about the item, and explains what you get access to when you purchase it.