- Build walls/garrisons everywhere. The AI can see through the fog of war, and it will march across a whole continent to burn down your unwalled towns.
- All the DLC for game 1 carries over to game 2. Game 1 itself functions as DLC for game 2, unlocking the super-campaign with all the factions in it.
- Don't play Wood Elves, Beastmen, or Warriors of Chaos; their campaigns are all pretty trash in their current implementation. The devs are slowly updating all the factions (last week they fixed the greenskins, who were previously unplayable), but for now those three are all bad. Wood Elves and Beastmen have fun unit rosters, at least, and all three of them are viable in MP, but the campaigns are not fun to play.
- There are no essential mods. However, there are a lot of tweaks to take the edge off annoying features (for instance, one that disables assassination, or one that imposes a cost limit on all armies so that neither you nor the AI can field death-stacks). Play the game vanilla, at least at first.
- The Skaven feel kind of bad to play without one of their DLC unit packs (either the Prophet & the Warlock, or the Shadow & the Blade). Outside of that, all DLCs are optional. They fall into two categories: a race pack (that makes new factions playable), and a lord pack (that introduces a pair of new characters, with unique starting postions, and adds some new units to two of the faction rosters). The DLC works similar to something like CK2: your game contains all the DLC stuff, but until you buy it, only the AI can use it. So, the Vampire Coast factions are in the game no matter what; buying their DLC just makes them playable. In other words, there's no point in buying a race pack until you want to play as one of those factions.
- Some of the "Starting difficulty" descriptions are... optimistic. The easiest, most straightforward starts are probably Tyrion and Malekith.
- There's no in-game way to trade land. So if, for example, some orks burn down one of your towns, and then one of your allies immediately resettles the ruins, there's no way to peacefully reclaim that land. You need to either attack the ally, or hope some mutual enemy will do it for you; it sucks. I believe there are mods that let you trade land. The AI doesn't value it properly in trade deals (which is why the devs removed it from the series ages ago), so it's kind of a cheat mod; you just need to restrain yourself.