Anyone can plaster a ceiling, but doing a good job takes care and practice. Once you get into the rhythm of it, though, you may find that plastering is fun. The basic technique for plastering a ceiling is the same as for applying any other wall or joint compound: Run the knife across the surface in smooth, even strokes, and don't lay it on too thick or the plaster may crack when it dries.
Cover the floor and furniture completely with a dust sheet.
Scoop plaster off a hawk or out of a pan with a 6- or 8-inch joint knife, then run the edge of the knife along the edge of the hawk or pan to clean off excess compound.
Cover the seam in compound by running the knife over the seam at an angle, so the edge of the knife smooths the compound as you apply it.
Use the edge of the hawk to scrape the plaster off the knife, then run the clean knife over the compound to further smooth it.
Cut a piece of drywall tape as long as the seam. Place the tape over the seam and gently press it into the compound, taking care not to wrinkle it. Run the clean knife over the tape and compound to smooth it out, pressing out any air bubbles. If part of the tape's edge is lifting up, use your fingers to fill the gap with compound, then smooth it with the knife.
Repeat for each joint. Wait for the joints to dry, then sand down any rough patches with a fine grit sanding block.
Apply a final thin layer of joint compound over each seam, overlapping the tape by an inch or two on each side. Smooth the compound with a clean knife, going up and down then side to side, so the edges of the compound are flush with the wall. Be careful not to gouge the compound with the edge of the knife. When the compound is dry, sand it smooth with a fine grit sandpaper.
Apply the first layer of heavy plaster, called the rough coat, using a hawk and a 12-inch plasterer's trowel. Use the trowel the same way you used the joint knife: Load the trowel with plaster, then scrape the edge of the trowel against the edge of the hawk to clean it. Apply plaster by scraping the trowel across the bare ceiling at an angle, so the edge of the trowel scrapes the plaster smooth as you apply it.
Work your way across the ceiling in sections. Start from a corner, go all the way across, then move down to the unplastered area and go across the other way. When you've applied plaster to an area, scrape your trowel clean on the hawk, then use it to smooth the plaster you just applied. Maintain a light, even pressure on the trowel to keep the plaster smooth and consistent.
Wait for the rough coat to dry completely, then sand it smooth.
Apply the "skim coat," a thin finishing layer of joint compound, over the rough coat, employing the same technique you used to apply the rough coat. This is the final coat, so take special care to keep it smooth and not to gouge the plaster with the trowel. When it's completely dry, sand it with a fine sanding block.
Apply a second thin layer of skim coat if the first layer is patchy or has gaps. Depending on how rough the rough coat was, it's common to need a second or even third skim coat layer.
Your two options for holding the plaster are a hawk and a mud pan. A mud pan is a rectangular metal basin that you can fill with plaster. A hawk is a flat metal panel with a handle on the bottom. You keep the plaster in a big dollop on top of the hawk. A hawk is a little trickier to use, but once you get the hang of it, it's faster and easier than a mud pan.
Always wear a mask when sanding.