In addition to what Gruntage said about intro and pressing ESC key, I can tell you there is little trick to make skippable cutscene(s) within the mission (with some notes to bear in mind)!
It is easy man: you just need to create radio trigger (e.g. Juliet, which you comfortably call by pressing twice 0 key) and set "TERMINATE" camera effect so, everytime cutscene is running, you double press 0 and it will immediately stop. If you plan to make several skippable cutscenes, then don't forget to click "Repeatedly" in the activation field next to "Juliet" so you can continue using this radio call more than once. This trick is good if you plan to make what I call 'descriptive' cutscene that is a camera that flies around units, vehicles, objects etc. when they perform cycled action (e.g. sitting down, patrolling, standing idle etc.) or when they just stay where they are for cinematic purpose.
- Does it necessarily have to be "descriptive" cutscene?
- Yes, because negative side is that this trick just stops camera but not the rest of .sqs script. So, for example, if you put a top view of NATO soldier shooting USSR soldier, you may stop viewing that sequence from top position but you cannot prevent first soldier from shooting the second one.
Anyway, I think they can be found many workarounds to overcome this limit but finding them it depends from the body of your camera script and from what you want to show within cutscene.