Begin to prepare the jacket for its final press by pinning all the way around the collar and front edges. As you pin, work the seam toward the back. Remember that the back is going to change at the break where the lapel turns.
Now go back and baste the edges into this position with long diagonal stitches. I am strongly biased toward silk thread here as it will not leave any impression on the fabric when pressed. Don't use any knots, just take double stitches when you need to end or start a length of thread; you want to keep everything smooth.
Now go to the ironing board and press, press, press those edges. Work it as much as you need to to get everything looking smooth and consistent, shaping the jacket as you go. I've been known to spend a good 45 minutes on this step alone :-) Use plenty of steam if your fabric can take it, a press cloth if it needs it, and instead of using the clapper here to flatten the edges, press with your hands or a pressing mitt.
If the hem wasn't turned up previously, turn it up now and carefully catch stitch it in place with somewhat loose stitches. You want the hem to be able to move with you as you move when you're wearing the jacket.
Once my hem is stitched down, I go back and use an invisible stitch to secure that bit of Hong Kong facing that is going to peek out below the lining.
Pin the folded-back lining hem edge to just below the catch stitching on the outer hem. Sew the lining in place with a fell stitch or slip stitch. This will create a jump hem, and you'll see those last few open inches at either side. Invisibly stitch these down to the facing.
Push the lining sleeves into the outer sleeves, then turn the entire sleeve inside out and fell stitch the lining hem just below the catch stitched hem you made on the sleeves previously.
Now in order to keep the collar in place, you have to stitch in the ditch again. You'll be stitching from shoulder seam to shoulder seam at the back neck, zigzagging from inside to outside. I admit this part is really tedious - you have to kind of fish around with your needle for each stitch to make sure you get it right in the seam. If you don't, the stitches will show.
Down to the wire now: mark your buttonhole positions and make the buttonholes, then cut them open and sew on your buttons. If you find that your basting around the edges is in the way when you are making the buttonholes, remove it first. Otherwise, remove the basting at the very end. Or not - you have some leeway here. I usually keep it in until I absolutely have to remove it.
Give the jacket one more light press and steam to work out any wrinkles from handling . . .
Go wear your beautiful new jacket! Or just sit there and admire it for a while. That's what I do ;-) I always keep my newest makes hanging from the dresser knobs like that so I can admire them for a while before putting them away in the closet.