When writing a story from multiple viewpoints, I find it helpful to concentrate on one character at a time. That way I can really get into his or her head and trace the story line as it plays out for them. Maintaining the proper chronology seems easier as well. This is most common for secondary/supporting characters as opposed to your protagonist, who is driving the story.
I tend to get ideas for scenes that don’t necessarily fit where I am writing, especially a first draft. In other words, I don’t start with Chapter One and proceed in order. When an idea comes, I need to get it written right away, or it will evaporate. This works for me, but does require paying attention to the story’s timeline and keeping everything in the proper sequence. My main point is not to ignore an idea when it comes your way. They can be fragile and disappear if you don’t capture them when they’re fresh in your mind.