If DCS takes your child usually the court will appoint a guardian ad litem.
The guardian ad litem is the attorney for the child. Their job is to investigate and advocate for the child’s best interest. They are supposed to “argue” their case (put on witnesses etc) just like the other lawyers involved. It is not their job to “protect” your parental rights. Instead they are to focus on their client (the child).
The courts I practice in give a good deal of weight to what the guardian ad litem says.
For this reason it pays to be nice to them. As part of their investigation they may want to talk to you. If you have an attorney the arrangements to do this should be made through them and they should be present when you talk to the guardian ad litem because the guardian ad litem (like the caseworker) can use anything you say against you. If you do not have an attorney you should be aware that anything you say can be used against you and say as little as possible.
Which brings up a point. Your discussion with the guardian ad litem is not the time to be shit-talking the other parent. The other parent may be a lousy parent and a worse person. But it is YOU, not them, who you are trying to get your kid returned to. Think about it this way. If you spend the whole discussion complaining about the other parent what REASON have you given the guardian ad litem have to want to return the child to YOU? If the guardian ad litem asks about the other parent and you have concerns about the other parent then mention them BRIEFLY but do not focus on them. You are trying to convince the guardian ad litem that YOU are an appropriate parent.
Also, the guardian ad litem may want to visit your home. Again, if you have an attorney they should be involved. But, at any rate, you need to be sure that 1. you are actually there when you say you are going to be there and 2. your house is CLEAN and free of any obvious safety hazards. I once did a home visit where the parent had a gasoline container sitting right beside a radiator heater. If your house is clean you can ask the guardian ad litem to take pictures of your clean safe home (everyone these days has cell phones that can take pictures) and the pictures can be shown to the judge in court to give them a better idea of what kind of home you are asking the child to be returned to.
At the end of the day what the guardian ad litem wants carries a lot of weight with the court and you should want them to want to return your child.