I love working with threads. A thread is one line of plot, an individual story separate from but interspersed with other lines, other stories of the plot. I like to break my books into two or three main storylines, further divided into threads and weave them throughout the book.
Like anything else, writing with threads has advantages and a disadvantage. I say “a disadvantage” because I can only see one, so let’s get that one out of the way straight off. The disadvantage is that some people don’t like a storyline to leave the character they’ve met, and move on to another they don’t know about yet. I am, of course, talking about that first break away – and I must admit, I’m a bit like that myself as a reader. Usually, though, I’m like that if the first part of the first thread is lengthy and I figured I was there to stay. The thread is always broken at an interesting point, and the first time you’re tossed out of that and into “somewhere else”, I – as a reader – don’t want to go there.