In music, dance, theatre and cinema creating a good, satisfactory beginning or ending is more difficult than composing the middle part, because, as in chess, the number of possibilities is limited. Just listen to the final seconds of a random selection of songs on your iPod.
Some readers commented that surely if the number of options is small choosing what to do is easier than when choices abound. That may be true in everyday life, but not in the arts. If the number of possibilities, that is the degrees of freedom, is small, doing something original or otherwise interesting is more difficult.
Metaphorically speaking, in terms of punctuation marks a piece could end with a . an ! a ? multiple ... a , or
In dance, assuming that the performance takes place on a stage, one possibility is for the dancers to simply stop dancing. At some point the audience will assume that the piece has ended and either start applauding or leave. Another possibility is to have all dancers leave the stage at once. We would still have to decide which side, but that's a detail. We could also have the dancers leave the stage one by one, in pairs or random groupings. We could alternate the side of the stage where they leave or have them all leave on the same side.
We could also end the piece with a Bang. This is the sort of ending that you can find in much classical ballet and in the work of George Balanchine. It is usually synchronized with music that ends with a grand finale and a bang. The Bang is essentially a dramatic variation on the dancers suddenly stopping or freezing in mid-motion. Instead of stopping at a random moment within a movement sequence the end position and the movement towards it is choreographed.
Another possibility is for the lights on stage to either gradually dim or to be switched off or for the curtains to come down.
In music you can sometimes almost hear the composer struggling with the ending. Again the music can just stop, the musicians can stop playing, either all at once, or one by one. This is what you can hear in many songs where the instruments are gradually removed. But by far the most popular ending in much contemporary music (pop, techno, r&b, hiphop etc.) is the fade-out: simply lowering the volume towards the end. Except that of course this is hard to reproduce live. It also feels like throwing the towel into the ring, admitting that you don't know how to put an end to it.
On a philosophical note, in real life, the end is the beginning is the end... The sun may set, but the next day it rises again and the end of the day is just the beginning of the night when a number of other creatures come to life. The Grand Finale in literature, cinema and sports creates the illusion of an ending, when in reality life just goes on.
While a Grand Finale can be gratifying and an open end very frustrating, I myself tend to favour non-endings. For example, what I liked about Gravity's Rainbow by Thomas Pynchon was the fact that at some point the main character for several hundred pages, Tyrone Slothrop, just vanishes, while the book goes on. What happened to him? His disappearance from the pages of the book could be interpreted as a metaphor for him getting lost in Northern Germany in the final days of World War II and the author losing track of him. It could also be interpreted as a metaphor for the total disintegration of Europe at the time.
The final page of the novel is equally fascinating as it evokes a number of endings and end metaphors. A rocket is about to hit a cinema. This by the way matches the opening scene of the novel. An audience is waiting for a film to start. It takes longer than usual. Perhaps the film has broken. The audience is restless. There is time for them to touch the person next to them, or, oddly, for a song to find them, a song which ends with the line "And a Soul in ev'ry stone . . . .". This is the penultimate sentence. Before that we have been told to "Follow the bouncing ball" as the lyrics of the song are quoted. The final words of the novel read "Now everybody—". A novel that ends with a — indeed