How Does a Judge Decide Who Gets Custody?
There are generally two types of custody in Alabama. Legal Custody is what people generally think about when they think about custody. This is usually granted to both parents, absence any history of abuse, neglect, or other such excuse. Joint legal custody means both parents are the legal custodians in the eyes of the law and are raising the child together as the parents. Sole legal custody would mean that one parent has no say in how the child is raised and might have no visitation as well.
Physical custody is where the child actually physically resides. The party the child actually lives with most of the time has sole physical custody and the other has visitation and pays child support, but the parties both have joint legal custody in this scenario. 
Having shared custody means the parties are splitting time equally with the child such as one week with one parent and next week with other parent and so have joint physical custody. Having joint physical custody is what is sometimes referred to as shared.
Custody cases are some of the hardest decisions judges have to make. Judges have broad discretion in awarding custody. However, Alabama law does offer come guidelines for judges to consider and rules to follow in making their judgment. The court is allowed to award custody to the mother and/or father after examining the moral character and prudence of the parents and the age and sex of the children. The court may award joint legal or physical custody (i.e., custody to both parents) or sole legal or physical custody to just one parent. Your child custody attorney will argue your case in front of the judge, but he or she will need to be able to show that whatever you are wanting is in the best interests of the child.
“The best interest of the child” is the standard the court uses in determining custody. Ala. Code § 30-3-152 states:
The court shall in every case consider joint custody but may award any form of custody which is determined to be in the best interest of the child. In determining whether joint custody is in the best interest of the child, the court shall consider the same factors considered in awarding sole legal and physical custody and all of the following factors:
(1) The agreement or lack of agreement of the parents on joint custody.
(2) The past and present ability of the parents to cooperate with each other and make decisions jointly.
(3) The ability of the parents to encourage the sharing of love, affection, and contact between the child and the other parent.
(4) Any history of or potential for child abuse, spouse abuse, or kidnapping.
(5) The geographic proximity of the parents to each other as this relates to the practical considerations of joint physical custody.
(b) The court may order a form of joint custody without the consent of both parents, when it is in the best interest of the child.
(c) If both parents request joint custody, the presumption is that joint custody is in the best interest of the child. Joint custody shall be granted in the final order of the court unless the court makes specific findings as to why joint custody is not granted.
According to Alabama law, every custody case is eligible for consideration of joint legal custody by default. Whether or not a judge decides to award joint custody of either kind is based on the requests of the parents and his or her review of the case, which involves considering the questions above. 
All of the considerations on the list above are equally important. If both parties request joint custody (joint legal), unless the court finds a history of abuse, neglect, substance abuse, etc., then joint custody is usually awarded as it is generally considered to be in the best interest of the child to have both parents in their life.
If you want to request sole legal custody of your child, you will need to explain to the court why you are requesting sole custody. This is because you are depriving your child of time with their other parent (the law generally prefers joint custody) and, if you win, you are depriving a parent the right to their child. Due to the seriousness of this, the court will want to see evidence that living with you would be so much better for the child that any downside to not having the other parent involved is outweighed by what you can offer the child.
For example, if the other parent has a history of abuse, substance issues, neglect, or recklessness then that might be a good reason. If there is a documented history of domestic violence in the home the court will generally take that as a rebuttable presumption that your claims are accurate. However, the other parent will have an opportunity to tell their side of the story as well. It is usually best to have a custody or divorce lawyer represent your interest and argue for you at custody hearings. If you contact a local family law attorney in Alabama, they can file your divorce and ask for custody or file for custody in non-marital cases as well.
You can file a Complaint for Divorce in the Circuit Court of 1) the county where the Defendant resides, 2) in the county where the Plaintiff resides if the Defendant is not a resident of Alabama, or 3) in the county where the spouses resided at the time of separation. For the Complaint for Divorce, you’ll need to have the following information available: Name, age, and residency of both parties; names of minor children and their dates of birth; grounds for divorce; marriage date and date of separation; acknowledgment that the parties have assets and debts for division; a plea for the court to take jurisdiction of the case and provide the requested relief.
If you cannot come to an agreement with your spouse over the terms of the divorce, the divorce will go to trial and the judge will make a decision for you on the unresolved matters.