Aside from the obvious:
-Gating.. make sure only one thing is going on at a time. If stuff doesn't overlap, it can't clash
-Delay: as in delay the whole subbass track a bit.. if your kick and sub are hitting at the exact same time, that's an awful lot of low end energy. It basically means they both can only be half of the maximum volume.
So offsetting the entire subbass part a tiny bit so it hits just after the kick saves you a bit of headroom.
-Harmonics: suppress the root frequency and boost the harmonic frequencies.
An old trick I used was to run the sub through a reverb, sample it, bring it down to mono and remove the reverb tail. What that does is introduce some harmonics from the reflection, livening it up a bit without
sounding like real distortion.
And the one thing to ALWAYS keep in mind when mixing sub is that (unless you have a really professional studio) you're dealing with frequencies that probably hardly even register on your kit,
and even then need a properly sized and treated room to articulate well. You're not supposed to hear subs, but feel them.. and you're probably not mixing at a loud enough volume for that (if you are, I pity your ears)
... all of that means you'll have a tendency to overdo them if you're mixing at home. Even on great speakers. If you blow it up to club size sound, it's gonna have way too much bass and sound muddy as hell: basscake!
So moderation is always key... even to the point of keeping it low in the mix and then enhancing it across the entire track (or sections of it). It's a cheap trick, but it can sound really good.