In theory, considering the needs of the children and the ability of each parent to meet those needs determines child support.
Parents who were just getting by financially, or who suffered financial problems during their marriage, will have substantial difficulty meeting the financial needs of their children after separation. Generally both the parents and the children will suffer some financial hardship.
The disparity of child support awards in the past spurred a trend to reduce child support to a mathematical formula. The South Carolina Department of Social Services prepared child support guidelines at the direction of the legislature. The major factor considered is the combined income of the parents. Expenses affecting the calculation of child support under the Department of Social Services child support guidelines include prior support obligation, the cost of health insurance for the children, the cost of day care expense if the custodial parent works, and other factors the judge considers relevant. The family court judge follows this guideline, unless he gives specific reasons for departing from it.
Each parent will want to prove the other's actual earnings. If your spouse is an underachiever or is under-employed then you may want to show that your spouse has an earning potential far greater than actual earnings. If a spouse willfully or voluntarily decreased income, then the court will consider ability to produce income, rather than actual income, in setting child support.
If you are a custodial parent, then explaining to the court the actual needs of your children is important. Showing special needs that other children may not require, such as braces, dancing lessons, or private school tuition, is effective. If you have been a good recordkeeper, then a review of your records will provide documentation of your children's actual expenses. The total of those expenses will probably surprise you. If you are a non-custodial parent, then explaining to the court how much money you will necessarily spend on the children for visitation is important. For example, if the children live in a different city or state, then transportation costs may be associated with visitation. You will probably spend more for housing so that the children can stay with you for visits.