I'm not an expert but I have been mudding since I was ten and have done
dozens of houses.
0) TWICE AS MUCH LIGHT AS WILL BE IN THE ROOM.
1) On the first coat I apply just enough mud to cover the seam tape, I do
not worry about tapering the edges. I also typically use a drywall compound
called sheetrock 90, that will dry in 90 minutes and is sandable.
2) Once dry I run around the room with the drywall trowel and give all the
high spots or bumps a quick scrape off, NO SANDING
3) I apply my second coat of mud filling in low area's and tapering the
edges of all the seams.
4) I sand very, very quickly.
5) I wipe all the walls with a damp cloth to remove dust.
6) I apply my final coat of mud, cleaning my trowel every couple of minutes.
A clean trowel makes the cleanest job.