You will need to mud and "sand" them, then paint them. Before doing that, check the source of the issue. You may have settling, which is most common, but there could also be issues with insufficient screws holding it in place. Make sure you remedy the cause before repairing or you will be having to do the repair over and over.
The reason I wrote "sand" is that I would recommend using a damp sponge and smooth out the mud.
Instead of typical sheetrock "mud" I would look into the latex muds now available on the market for covering cracks. They're easier to work with and they are lot less prone to crack once in place. Once covered sand lightly and paint over.
Here is some info
Hi Jay, sorry you have cracks in your ceiling Hope this helps you fix it. . Showing results for how to hide drywall cracks in ceiling
Search instead for how to hide dry wall cracks in ceiling
www.diynetwork.com › ... › Walls and Ceilings
You will have to get some dry wall putty and smooth it over the cracks. Sand flat when try and paint over those spots.
Here is how to fix several ceiling crack/seam issues: https://www.youtube.com/watch?v=yk6EvKpiG7U
Remove any weighty items in roof space or above ceiling. Tape the cracks with Plaster tape, or fill the cracks with Spackle or white cork filler using a Wallpaper scraper. Wallpaper the ceiling using a thick wallpaper for ceilings, tile or clad the ceiling. Best wishes.
You can always apply tin tiles, wood, acoustic tiles, more sheetrock, or follow the other cheaper suggestions.
Hey Jay: Check these sites for some help:
One thing to do, is to use a flat paint when you paint. Shiny paint shows every bump and lump there is.
Hello. Drywalling can be difficult and frustrating for the typical DIYer. The technical technique using spackle and a knife blade can be challenging. We’ve always hired out doing ceilings and wall board seams. Hope you find a satisfactory solution and competency doing this.
First, see if you can find why it's cracking. If it's a small crack, it's probably just minor settling but if the crack is major, you should have someone come inspect the house. After that, you can try spackle or joint compound and sand it. It may take a couple of tries to get it looking good.