Firstly, if a pattern has markings - use them.I use good old pins to mark dart and notches. I also mark the size I'm working on too because different patterns have different ease so I need to note this on the pattern. When I'm making lots of changes, I date them too.
I make sure there are pins on both pieces when I cut two layers at a time.
Here's the pin on the under layer.
Below are the pin marked darts.
This method works fine if you complete this work in the same sitting. If you're doing this over a few sessions, use a marker or use tailors tacks because pins can fall out - and they do.On the lining piece above, I've marked the start of the dart and I'll fold this into the seam but not sew it up, so there's some wiggle room in the lining.
There's a note to staystitch the front facing at step 16.
So again, I've used pins to mark the staystitch points.
Don't just look at what I've done, go to some real references.
Singer Tailoring - 1988,
Jackets for real people by Alto, Neall and Palmer - 2006,
New Simplicity Sewing Book - 1979
Easy, Easier, Easiest Tailoring by Palmer and Pletsch - 1977