Set Dressing

Set dressing, for those who don't know is everything on stage that isn't handled by the actors, but that serves to make the space look more full. This includes the pictures on the wall, the rugs on the floor and the books on the shelves. It also often includes the random pile of junk mail on the counter, the muddy shoes in the corner and the dishes in the sink.
Set dressing is regularly a headache and a challenge for the props master. It is often left until the last minute becuase the things that actors need to touch and work with are given first priority. It also really can't be completed until the set is, and if the set is being loaded into the space during tech, that means that by the time the set is up, time is at a premium and you will be fighting with lighting designers and actors for a time in the space to do your work. Don't be surprised if you end up doing your set dressing by the light of a small headlamp while the lighting designer is writing cues.
To make set dressing easier there are some things that you can do to prepare. First, take a look ahead of time at the set drawings to figure out how much space you need to fill (five shelves that are 3ft long hold A LOT more than five shelves that are 2 1/2ft long). Second, pull twice as much stuff as you think you need, if you need a cluttered or messy space make that 3x as much stuff. You will be surprised at how quickly your three boxes of kitsch will get used and leave you hunting for more stuff. Third, have all of your tools ready. My set dressing tools consist of a hand stapler, short screws and a drill, floral wire, double stick tape, a hot glue gun and rope caulk.
The hand stapler is good for tacking down fabric and papers.
The screws I will use for bigger items that I am allowed to damage, and for hanging pictures. People outside of theatre would probably be horrified at how often I put a screw right through the wooden frame of a picture rather than hanging it from picture wire or a hook. In the theatre though a screw is faster, won't be seen at a distance, and most importantly will prevent the picture from shifting or falling off if the wall is knocked.
The floral wire is great for pieces that can't be damaged, but need to be secured down. It can be wrapped around your item and then wrapped back to another item nearby or a screw placed for just that purpose. It can be especially effective if the piece you are attaching down has a hole that the wire can be wrapped through.
Hot glue is great on wood, plastics, metal and glass becuase it can be peeled off of these surfaces after you are done without causing much damage. It doesn't take much force though to get the hot glue to release though, so if the piece is going to be moved and jostled a lot you probably should go with something else. Also hot glue does not come off of or out of fabric.
By far my favorite tool though is the rope caulk. Rope caulk is essentially a sticky clay that never dries. You can use it on just about any surface. It is removable and reusable. To use it simply pull a bit of caulk off, roll it into a ball, press it onto the piece you want to stick, press the piece down onto the surface you want to stick to and twist slightly. The major benefit or rope caulk is that this can be repeated again and again. If you want to move the vase to the other table, you can do it in a second. If an actor decides to pick up a stapler on the desk he wasn't supposed to touch, he can do that without looking awkward, and when he sets it back down you can still be reasonably sure that it won't slide off when you roll the desk offstage in the next scene. It's pretty much a miracle tool, is cheap, and available in most hardware stores.