There are several factors a seller will consider.
1- The purchase amount- Obviously every seller wants the most amount of money, but that is not always the only consideration.
2-The contingencies- Typical contingencies are home inspection and mortgage. Remember you may be competing with people who have removed one or both.
3- The timing- If you are insistent on closing on a certain date that may not work for the seller.
4- Financing terms- If you are a 3.5% down buyer and someone else has 20% to put down or even paying cash, that will be hard to compete with. I will have sellers choose cash offers that are lower than an FHA financed deal.
5-Earnest money deposit- Put your money where your mouth is, understand how that can impact a seller.
6- Terms- The more complicated you make a transaction the more difficult it is for a seller to understand the deal. I have had buyers argue about curtains and furniture. Your buying a house not personal belongings.
7- Your demeanor- Always negotiate in good faith and carefully parse your words. Sellers can get offended about how you handle yourself. I have certainly had sellers kick buyers to the curb who handle themselves like a bull in a china shop. If you are competing with other buyers you can shoot yourself in the foot.
At the end of the day the home sellers want the most amount of money they can get, but they also want a deal that can close with few hassles. Good Luck!!