When I first started playing tournaments I would usually finish on a comfortable 4 or 5 Major Defeats. This was happening to me because I wasn't just a new player, I was a bad player. Losing doesn't make you bad, but losing consistently and not taking steps to improve does. My first step to improving was to read my warscrolls. Not just read, but really dig in and memorize them (Clan Pestilens has about 6 warscrolls, so no excuse not to really). From there I constructed a small phase by phase flow chart to remind me of all the small rules that I would sometimes forget that culd have shifted the balance of a game, and as soon as i made this chart i went from an average of 1 Major Victory to 3 Major Victories almost overnight. This can be applied to any army, but I've posted below the flowchart I was following for the NZ Masters tournament last year (Adapted for AoS2) where until Round 4, i was one of the favorites to win the event (Fate is fickle, ****** you Tzeentch).
Pestilens Turn Progression
· Choose whether to spend command abilities (not advised in the first battle round, save them for turn 2 charges).
· Use all prayers of all priests (If first battle round things won’t be in range of Pestilent Breath, however you can still do it targeting nowhere to potentially get The Neverplgaue great plague).
· Cast spells with the Verminlord Corruptor.
· Choose whether or not to use one-use only effects in the Plague Monk and Plague Priest warscrolls, ideally the Plague Monk tome that deals mortal wounds or the enemy debuffs from the scroll.
· Check if any enemies are within range of proximity-based damage (Plague Furnace, Plague Censer Bearers).
· Plagueclaw Catapults can move without a penalty to its shooting.
· Move Plague Monks and Censer Bearers forward, however if they cannot possibly make a successful charge stay out of enemy charge range or bubblewrap with Plague Monks that have the Rabid Fever prayer active.
· Prioritise infantry blocks with good saves as the Plagueclaw target, or soften up targets about to be charged by your Plague Monks.
· Verminlord has a shooting attack, it isn’t awful against low save units.
· Command points can be spent to reroll failed charges, so roll charges before spending the points.
· Charge in groups of 2 or 3 units, avoid sending you entire army in in a single phase.
· Remember that Pestilens allegiance gives you 2 bravery for every 10 monks in a unit, not 1.
· If you wish to use Inspiring Presence it has to be done before any battleshock rolls are made.
If you play Pestilens, I recommend taking this and adapting it to the list you run. If you don't play Pestilens (Normies leave reeee) I recommend constructing one for your own army regardless of how good a player you are. It only takes one lapse of memory to lose a game.