Procure the forms for temporary child custody from your county clerk. (Your county clerk's office probably has a website with forms available online.) Be sure to obtain the correct forms---there is a form for child custody if you are going through a divorce and there is a form for child custody if you are not going through a divorce.
Procure the forms for child support from the county clerk. If you are going for child custody, you will need to request child support. Some states may have a Motion for Child Support incorporated within the Motion for Temporary Child Custody.
Read the forms carefully prior to filling them out. There are certain requirements for different types of custody. Most states will not allow you to have sole custody unless the other parent is not fit for visitation. Each state will have its own requirements for sole custody. You may also request shared custody wherein you will be the primary residential parent and your spouse will be the secondary residential parent. The child lives most of the time with the primary residential parent and the secondary residential parent has reasonable visitation rights. Your state may have an outline for fair and reasonable visitation rights, and it will probably include rotating holidays and visitation at least every other weekend. Some states allow joint custody, wherein the child spends an alternating amount of time with each parent. If the parents live close to each other and are in the same school district, or if the parent who does not live in the school district agrees to transport the child to the school district, you can also request the court order shared custody. The child may live with one parent for a week, then a week with the other or the time frame may be a couple of weeks. It is generally up to the parents how they arrange joint custody, but it has to be in the best interests of the child and the court must agree that this type of arrangement is in the best interests of the child.
Fill out your state's Family Law Financial Affidavit. The financial affidavit will be needed to determine child support. Once this is filled out, you will be able to fill out the child support guidelines worksheet. Most states have a set formula used to determine child support. The formula is based on the parties' incomes and hopefully allows the child to continue to live in the manner he is used to living.
Fill out the temporary custody forms once you have an understanding of the type of custody you are requiring. Make sure you know the ramifications of your request. It is best if you can come to an agreement with the other parent---not necessarily for you and your spouse, but for the child. Custody battles can affect a child's well-being. If your spouse agrees with you on the custody issue, instead of filing child custody forms, draft a partial settlement agreement outlining the custody issues. File the agreement with the court, requesting the court's ratification of the agreement. If the court agrees that your agreement is fair to the child, the court will enter an order ratifying the agreement (this means that the court turns the agreement into a court order that both parties must abide by). You must still file the Family Law Financial Affidavit and the Child Support Guidelines Worksheet if you are signing a partial settlement agreement, as the court will use your incomes to determine child support.
Request a hearing date if you do not file a partial settlement agreement. You will then both appear before the court and the court will make its ruling and file an order that both parties must abide by. If you can settle the issue with a partial settlement agreement, it is best to do so, as the court may not grant all of your wishes in the Motion for Temporary Custody and Child Support.