We had some expensive interior doors installed. I am planning on installing the casement trim myself, a project I've done before, but want to pick some brains. Since the walls aren't perfectly plumb, in some areas the door frame stands proud of the wall. In these areas, I plan on fastening the trim to the door frame and making up the difference where the wall and trim meet with caulk. But, in the spots where the wall stands proud of the door frame, what is the best way to fit the trim so that it meets the door frame. That is, if I lay the trim flat on the wall, there will be a space between the trim and the door frame. The frame and the trim are stained clear alder, so caulk will not work to fill the gaps. Should I scribe the back of the trim and shave off the excess on the wall side? If this is the right way to do it, any tricks or special tools I should be using? Thanks!

You can shave the trim but the rest of the trim won't meet at your 45's perfect.Depending on the size of your gap mill a piece of wood to fill the gap glue it to the trim then use a hand plane to shave the piece flush when you nail it in place and stain it you will never see it.

Thanks, James, but I think you're wrong. If I only shave off the back of the trim where it needs it, and not the whole length of trim, the mitered edges should be fine. Anyone else out there want to help me with the best way to do the "scribe" technique, or offer a different alternative? Thanks!

If I think I understand you correctly, the jamb, sits proud at certain places and also is recessed at certain places?
I would add a 1/4" extention to the jamb(seeing 1/4" will extend the jamb past the high spots on the drywall. Install the casing using a short length finish nail to the jabs only. Shim the corners and low spots. Make sure you install shims, under the casing, where your nails will peratrate through the drywall into solid framing.