You have a job offer and you are seriously considering taking the job, but before you make any sort of commitment you’d like to see if you can increase the salary they are offering.
Make a phone call
Before the date you’re supposed to respond with your answer them call the employer and tell them:
I am interested in this position and I based on my experience and expertise I believe can bring X and Y to your company. I am wondering if you are set on the salary you offered or if there’s an opportunity to enhance it.
If they agree immediately thank them and let them know you will get back to them by the deadline. If you think they might be open to giving you even more you can say:
Thank you. I appreciate that. It will help me with my decision. Would you also consider X?
If they aren’t willing to go any higher then you can let them know you will respond by the agreed upon date. If they accept your proposal, you can either accept on the spot or say you’ll let them know on the agreed upon date.
Maybe yes maybe no
Instead of answering you right away, they might say they will get back to you. In that case ask for a date when you can either all them back or expect their call.
If they ask you what you have in mind you can ask them what they think is possible or else give them a salary range more in line with what you’re looking for.
Depending on their answer you can either accept right away or let them know you will respond on the agreed upon date.
No room for improvement
If they say no, you still may be able to improve the offer in some other way. You can say:
Instead of X would you consider Y (here you can talk about vacations/benefits etc.)
Remember they have chosen you. They like you and they believe you will be a good fit for their organization. Salary /contract negotiations are part of the process. If you never ask you will never know what the answer might have been!