Here's the shirt I'm currently working on, it's BWOF 10-2007-117; it has 4 long pleats on the front and 2 long pleats on the back.
First you mark the dart on the fabric (I use a fabric pencil), then you thread baste a "ladder" up the dart. This shows the right side of the front bodice, two pleats side by side.
When you pull both ends of the thread, the fabric will fold right sides together and the basting thread will give you a nice line to sew along
Up to that point, my darts had always been very sloppy and imprecise. I just folded the fabric and hoped for the best. This Threads tip showed me a very easy and precise way to make darts & pleats. So I've got to send a big shout out and thank you to Leona Butchart for submtting the Threads tip that changed my life! Now darts & pleats are easy peasy.