Overtime counts, too!
Many non-custodial parents think that child support is just calculated on his/her base salary. Think again! All income counts, so this will include overtime or income from a 2d job. As such, if the custodial parent threatens to sue for child support, you may wish to consider cutting back on overtime, or giving up that 2d job - or else you may be stuck with having to keep earning that income whether you like it or not.
Other forms of income count too!
Some people don't realize that if they have rental income, dividend income, or income from investments that it counts as income for child support purposes as well. Additionally, if you receive a tax refund, then guess what? That's income as well. The good rule of thumb to use is: any money coming into your wallet is probably going to be considered income for child support purposes. Be forewarned!