I have some projects I recorded in Sonar 8.3 that I need to send to a friend to mix. He uses Logic. What's the best way for me to send these tracks to him.
I've never done this before so, thanks in advance for any advice anyone can offer.
Also, can I expect this to be a difficult process? Ha ha!

The difficulty depends on how many tracks you have. Do you really need to send each track separately?
If your friend will, say, only add a guitar solo or vocals, you can send an MP3 to him, and he records his part in full wav quality, and sends those tracks to you to be added into the project.

Otherwise you must export every track as a separate wav, and your friend must re-assemble the project in Logic. In such a case it's practical to make every track start from measure 1, that way your friend doesn't need to manually position the tracks.

In case Logic reads OMF-files, you can export the project as OMF.
 
EDIT: Oops. I noticed you send it for mixing. Then you must have a mutual understanding about effects, for example. If you use FX, which are then printed in the wavs, it can be tricky for your friend to add more FX.

make every track start from measure 1, that way your friend doesn't need to manually position the tracks.

This is the key bit of advice, Rod. A wave file is a wave file regardless of the DAW, and 00:00:00 is 00:00:00. Using this method I've participated in group collaborations where participants used SONAR, Logic, ProTools and a hardware DAW, with the final mix done all-analog to tape. 


A Logic user will have to confirm this, but I believe it can import 32-bit wave files. If so, then that's the ideal format to send your files in. Otherwise, you'd have to export tracks as 24-bit files.

So Audio files are easy, but if your tracks are MIDI then you have to make a few choices. 
If you have a VST that he doesn't have then you will have to sort that out. 
Either bounce the MIDI track to an audio track or find a VST with a similar sound in his collection. 

Thanks for the advice everyone!
I'll be sending raw tracks : no FX for him to mix as he wants.
Also, no MIDI, just audio.

Rod I woul stem the audio and NOT OMF. OMF transfers can be a nightmare especially on limited studio time.

Hope this helps.