Before you start trying to come up with a signing bonus amount, know the ins and outs of the company you’re negotiating with. What types of bonuses do they usually hand out and how often (e.g., quarterly, end of the year)? What does a typical benefits package look like? How are raises determined and how often are you eligible for a raise or promotion?
If you know someone who’s already inside the company, see if you can get them to provide some insight. If not, research similar companies and check around with your network for their thoughts. Recruiters are often a good resource for this type of insider information.
Then, look at what you’ve learned in light of your current offer. Is the salary the company offers comparable? Does your benefits package seem sound? This will help you determine what kind of leverage you might have when negotiating for a signing bonus.