Many parents have differences of opinion regarding how to raise their children. Maybe one parent likes to let kids stay up late on weekends, but the other parent believes it's more important to be consistent with an earlier bedtime. You and your co-parent might have minor issues that cause friction between you. It's not uncommon, and it's often not impossible to find common ground on which you can build a compromise.
However, if you're heading to court for a custody battle in divorce and you believe you should get sole custody of your kids, you'll have your work cut out to convince the judge to agree with you. Most judges believe it's best for kids to have healthy, active relationships with both parents after divorce. If you think your ex's presence is a detriment to your children's well-being, you need to be able to support your claim with evidence.
Legitimate evidence versus trash-talking
Regarding evidence of unfit parenting, you can't simply show up in court and say a lot of bad things about your ex. In fact, most judges would look quite unfavorably on such tactics. The court is not interested in the fact that your ex never picked up dirty laundry off the floor or never thanked you for the kind things you did. Such issues are irrelevant in custody proceedings unless the issues you mention somehow place your children at risk.
Evidence of unfit parenting must include information about lifestyle, parenting behavior, direct negligence or abuse. For instance, if your ex is an alcoholic and you believe the problem would place your children in harm's way if they were to live with your ex part time or even have unsupervised visits, you'll need to prove to the court that the accusations you make about substance abuse are true.
Other factors that might prompt an unfit parent ruling
If your children suffer physical, emotional or sexual abuse at the hands of your co-parent, the court would definitely want to further investigate the situation. Witness testimony may also be a key factor what influences the court's decision. Other problem issues that suggest a parent is unfit might include a serious gambling problem. If your ex goes out all night partying and gambling and young children would be left alone, the court would want to know about it.
Any factual information or evidence that shows your children are safer and better off solely in your care is something the family law judge would take into consideration when ruling on a sole custody petition. If you're not sure whether you can build a strong enough case, it's helpful to speak with a family lawyer who is well-versed in such issues.