Simple:
* The seller offered a discount on the item.
* The seller was friendly and helpful.
More Complex:
* The seller of the house was eager to close the deal.
* The seller's reputation for quality products attracted many customers.
* The seller promised to deliver the goods within a week.
In a specific context:
* The seller of the vintage car was a knowledgeable enthusiast.
* The online seller had a wide variety of products to choose from.
* The seller at the farmers market had the freshest produce in town.
Remember that the context will determine how you use "seller" in a sentence.