I’m setting up my AstroMaster equatorial mount. Should the declination (DEC) slow motion cable (control) point towards the front or rear of the tube?

Yes, towards the rear or mirror end of your scope is the usual position for the DEC control.

However, because the scope is mounted inside tube rings and it has a dovetail mount, you can position it the other way as well.  That may give you a more convenient position for eyepiece viewing. 

Updated 12/25/13