Don't get silly and try to write a multi-threaded novel straight off, you'll tie your own shoelaces together and trip over them. If you must do multithreaded, a better way to do it is to write a novella -- say, 30,000 words long -- and then write a second novella of the same length showing the same story from a different angle. Then intercut them chapter by chapter, like chunks of salami. The trick here is to find a story that has enough different angles to be worth looking at repeatedly.
One of the easiest and commonest character development McGuffins is the romantic engagement or "boy meets girl" plot. The conventional rendering is "boy meets girl, boy loses girl, boy finds girl". With or without variations -- in the case of my most recent novel, "boy meets six-armed alien penguin, boy and six-armed alien penguin have great sex, boy turns into girl, girl loses six-armed alien penguin ..." -- it's a handy tool because it gives your protagonist a goal to aim for and a yardstick for character development. By the way, people have been running riffs on this since the 16th century (and earlier); Shakespeare's comedies are a good source of ideas, notably "As You Like It", "All's Well that Ends Well", "Much Ado About Nothing", and so on. As somebody or other said, "if you're going to steal, steal from the best" -- there's a full run of synopses at http://www.bardweb.net/plays/ that provide a suite of off-the-shelf romantic subplots if you're not imaginative enough to work out the details of six-armed alien penguin sex with hermaphrodites.
And more along those lines. One day, I might give something like that a try (writing a novel, I mean, not hermaphroditic alien penguin sex). I keep coming up with ideas, timelines and scenarios, though not quite enough for a novel.
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