I think perineal massage is probably a lot like pelvic floor exercises... probably helps if you actually do it religiously. I gave it a halfhearted attempt but was just too big and uncomfortable to do it properly.
I think I mostly tore because I was so out of it I just puuuushed as hard as I could and ds shot out. I think it was probably unavoidable because of that.
If you're worried, talk to the midwife who will be delivering your baby and ask her for extra support to try to prevent tearing - they can hold a hot damp flannel against the perineum to allow it to stretch more as the head crowns.
But don't worry, having torn and been stitched up, I can tell you that it isn't as bad as it seems. Tears happen at the very peak of proceedings, and everything is so stretched and you're so concentrating on getting the baby out that it's a bit like running through a field at full sprint and then only noticing you're covered in scratches from the bushes when you stop running (hope that makes sense)
The midwife had to tell me I'd torn as it was all just part of the soreness afterwards (which you're usually barely aware of anyway at first because you're too busy gazing at the baby!) and the stitching wasn't fun but again not the end of the world, and you can ask for plenty of local anaesthetic, or if you have an epidural you won't feel the birth, the tear, the stitches, anything! My option for next time)
And afterwards, the tear is still just part of the soreness, I was fully healed in 3 weeks. So try not to dread it too much, it honestly isn't that bad! hope this helped.