OK, I have a friend that wants some of my tracks to mix but he's working in Protools. I know it's one of the audio export functions but what will make it easier for him to import? Number 2, Other than mailing a DVD of data , what file sharing services are you finding easiest for music production sharing? Thanks.

reasterday
I know it's one of the audio export functions but what will make it easier for him to import?

 
easiest is to export all tracks from start to end. so he simply pulls them in, all are aligned and off he goes ...
 
checking "Export Broadcast Wwaves By Default" in Prefs/File/Audio Data also helps in case not all files are bounced front to end.
 

reasterday
Number 2, Other than mailing a DVD of data , what file sharing services are you finding easiest for music production sharing? Thanks.

dropbox. fast and easy. gives you up to 2 GB or so ...
 
in the creative phase sharing MP3 exports is a lot faster and sufficient. when mixing you need to use full resolution WAV files (24 bit, no downsampling, no dithering)

Thank you sir, greatly appreciated.

Yes, simply export the tracks as WAVES and set up a shared Drop Box folder.  Using drop box is faster and easier than burning a DVD.
 
I work with some other studios every now and then and they have PT and I have Sonar.  We simply use Drop Box to exchange wave files and everything works perfectly.   Wave work in practically every DAW on the market without any issues.
 
Just be sure to export the entire wave track from start to finish. Don't think you're doing a favor for your friend by trimming it. Don't ever trim it.