What or which costs incurred by home seller are tax deductible? Thank you.

In general, you can include various kinds of the property selling expenses in the cost basis of your property, increasing the adjusted cost basis of the property and decreasing your capital gain. Any reasonable and customary expenses to get your house sold are your properoty selling expenses. For example,all those fees, commissions you pay at closing, plus any capital improvements that prolong the useful life of your property.
Keep thisin mind; as a married couple, you can exclude up to $500,000 of long term capital gain as long as either spouse owned the home for at least 2 of the 5 years before the sale. Or neither spouse has used the exclusion during the prior 2 years. Also, suppose you have co-owners (for example two unmarried co-owners), each owner can take his or her exclusion of $250,000 respectively.