* First, make a copy of your project if you don't want to destroy it.
* Set the global tracks Setting to the bit depth you want, say 24bit at 44k1Hz
* Bounce down tracks to create the stems you want. Bounce even single track stems, to remove any trimmed Audio.
* Delete the original tracks.
* For those bounced stems that do NOT start at the beginning of the song, Stretch the beginning of the bounced track to the start of the song and bounce again. This is important because the engineer cannot guess where the stems are supposed to start, so here you are adding blank space between the song start and the beginning of, say, a guitar solo stem. Note that stems may be shorter than the song.
* Copy your Project to another Folder, first checking "copy Audio" (Default, I think). This will copy only those tracks that are in your Project (not the snippets still Floating around in your Audio Folder)
* If you now look in the Audio Folder in the new Project, you should find all stems, ready to be sent.
* Finally, name and number each stem so it will make sense to the engineer.
That's how I do it.