ceemdee

If you think your carving is going to take a while (more than one day) don't cut the pumpkin open and clean it out right away. You can do a lot of the major carving before you'll need to test it with a light and the pumpkin will last longer. The downside is that the pumpkin will be heavier and the stem might get in the way (which you do not want to damage).

Out of context, talking about pumpkin carving can sound rather disturbing.
Cover work area in plastic. Remove the guts. Cutting will make it "bleed". Cut, dig, remove pieces of skin. Scrape the flesh down. Don't worry about getting messy. Then later on when it starts to smell just throw it in the woods.

Don't worry about getting bits of pumpkin gunk on your light bulb, burning pumpkin smells delicious.

The curvature of the pumpkin can make it difficult to apply a flat stencil so try to cut away as much of the unused area as possible. This includes cutting out the center of areas that won't be carved, not just around the edges. Cut the stencil into different pieces and apply them separately if you still can't get the stencil to lay flat. However this may change the look of the design a bit. Pieces may be closer than they look on the original stencil or may even overlap each other. You can also warp the stencil itself. Something like the "Inflate" (negative percent) effect in Illustrator or the "Pinch" effect in Photoshop can help reduce the curved look. This works especially well for designs that have a lot of straight lines.

Super glue two X-Acto blades together and jam them into the knife handle. There is enough of a gap at the tips of the blades to cut really really thin lines. Then use the head of a large needle or a very small screwdriver to scrap out the line.