I was going to patch up this post, but I decided to do a new one. The old one is mostly right, I just wanted to add...
• In AC9, there is a menu command for Create Independent Detail. That means you can have a shortcut for it. In our keyboard setup, it's Ctrl+D. (What. Oh. Tools menu. Please don't do it that way. I hate menus.) Also nice, when you create an independent detail, it opens automatically.
• For some reason, most of my projects open new independent details at absurdly zoomed-out views. Like the window is a million feet across. I can't fix this, it's not stored in the prefs. It's always a good idea to work near the origin. You can zoom to the origin quickly by placing an object there and then doing a fit it window.
• Wall sections should be Sections. It's so clear to me now.
• IDs. They still need to be unique, but the ID will now take up to 31 characters, so you can be very non-cryptic. You can have spaces, though I don't use them. I like it to be clear that the first word is the ID. To review, use the ID to say what type of detail is in there, with a number so maintain uniqueness. Use the name for a fuller description. Eave1 Typical, Eave2 Shed, Eave3 Porch.
I have been drawing all the engineering details myself, based on their sketches. I keep these separate by beginning all their IDs with "S_".
• Detail markers: For areas, use Detail Area JAM9. For flags, use Detail Flag JAM81. These markers show the ID in Archicad and the drawing/sheet number in PM layouts. For assemblies, use Assembly Marker JAM81. This marker maintains the ID, which is the same as the (non-autotext) drawing number in each assembly detail. It also gives the sheet number, which is automatic. I have developed the habit of putting my schedules and assemblies on sheet A3-1, so they stay put as sheets are added.
• Remember you can open a detail from any marker, not just the original one.
• The biggest hassle with the detail tool is the fact that you can't put a detail marker in a detail window. Maybe someday. If you need to call out a detail within a detail, use an object. Remember the autotext referencing hack.