Here are some of the most common matchups you'll face in the current meta.
R/W Vehicles
This is probably the toughest matchup and mulliganning for a good draw is crucial. In the opening hand we want to see Radiant Flames or Flaying Tendrils and our two mana kill spells either Immolating Glare or Blessed Alliance. Turn 1 Authority of the Consuls is also a huge power play here. We definitely win in the late game, so just make sure you have the cards to get there.
Sideboard:
This matchup is actually deceptively easy for us, we have a lot of ways to deal with both
Ulamog, the Ceaseless Hunger
and Emrakul, the Promised End. Not to mention how inconsistent that deck can be. Using Nahiri, the Harbinger to keep them clear of
Aetherworks Marvel
is useful but we don't actually care about the artifact, especially post side-board.
Sideboard:
This is a decently tough deck, however we have a silver bullet in the sideboard.
Cataclysmic Gearhulk
is our worst nightmare, so whenever possible try to exile that one. Other than that the only thing that is bad is
Combustible Gearhulk
can kill walkers on entry so I usually let them draw since they want their cards in the graveyard anyways. A sustainable Nahiri, the Harbinger and Authority of the Consuls can be amazingly powerful in this matchup.
Sideboard:
This matchup can be a bit iffy as we can't interact in game one and they can't really hurt our walkers unless they counter them. Dynavolt Tower can be really annoying if they get it online so keep a Nahiri, the Harbinger in hand so once they tap it you can remove it. After sideboard you can expect them to bring in a couple creatures so keep the straight kill spells in as they either have other modes or are in low enough quantity that it's worth it.
Sideboard:
This matchup in its various forms is easier than you think. Negate and
Void Shatter
are the only two spells they have that we care about. Chandra, Torch of Defiance really shines in this matchup because once she lands her mana ramp allows you to play more spells and planeswalkers per turn than they can counter usually. A key trick here is to bait out the counters, play the spell you really want last and then run away with what ever manages to stick. Also remember, most of our walkers beat Torrential Gearhulk so even if they take a hit it isn't horrible.
Sideboard:
Most of the rest of the decks either aren't good enough to mention or aren't big enough. Temur Colossuss is shut down by our kill spells and Authority of the Consuls. Electrostatic Pummeler on turn 3 is beat by a Liliana, the Last Hope on turn 3 every time, not to mention Blessed Alliance doesn't care about their hexproof trampler. U/W Flash may see a resurgence because of the guy in the top 8 but I actually haven't played against it because no one is playing it currently.