How does one reduce the size of a wav. file? I need to squeeze some projects down in size.
I would rather not erase tracks. Most of my project files are 10-12 tracks. 40-65 meg.
Convert tracks to mono wherever possible. Many people record mono sources on stereo tracks, this will obviously create files twice as large as necessary.
Not sure what bit depth you are using, but if you are at 24, consider using 16, as 16 bit files are considerably smaller.
A 10 minute 24 bit stereo .wav is 164 MB, whereas a 10 minute 16 bit stereo .wav is 109 MB.
Cheers.
Bounce down to FLAC is another option if you can handle the quality… still way better than MP3 @ 320 IMHO
Cubase can record natively in FLAC too, so you could experiment with starting out that way also.
What the other guys said will keep you in WAV though, those are the best suggestions.
Switch to 15ips
Thanks to all
remove unused files empty trash , then in the pool select all tracks and right click and choose minimize if you dare, it`s ok just do it ,it erases the parts not used .
Reely? 
Why not 1.7/8 ips 
Ah the good old cassette tape.
Or you could consider like buying a hard drive or three?