Well not much to be honest.
AdMech (mostly Skitarii):
- ignore the Techpriest since he is too hard to crack and can heal himself every turn anyway. He doesn't do much on his own either
- try to tie up Onager, Techpriest and similar shooty units in melee asap...and stay there unless you are sure you can nuke that unit this turn!
- Nuking Kastellan with Longstrike and Seeker Missiles turn 1 is actually quite viable
Tyranids (haven't played against a list with brains in 8th yet):
- try to get rid of Warriors and Hive Guards as fast as you can. They carry a Tyranid army due being durable infantry (yes they are infantry), with decent/good weaponry and Synapse.
- big monsters look scary but our Suits can tank them in melee quite some time actually. Especially with Drones nearby.
- don't underestimate gaunts but also don't make them a high priority target
- focus fire on mean and fast melee units and keep the shooty ones busy with Stealth Suits and Vespid (so basically as always
That's pretty much my regular group. We have Astra Militarum, Deathwatch and Harlequins as well but I haven't played against those yet.