Don't be apprehensive about reorganising your village according to your circumstances - if you want to build up masses of Gold or Elixir for your next upgrade, rearrange things to fully protect your reserves and Mines / Collectors (even at the expense of Castle / Town Hall if necessary). You can always screengrab your current set up should you wish to return to it.
Train troops or Spells while simultaneously upgrading them in the Laboratory but time it so your units or Spells are generated before the upgrade is finished. Those units / Spells will get automatically upgraded, meaning you get higher-level troops / Spell at a pre-level-up cost!
Upgrading your storage units, aside from making it possible to save up larger amounts of course, also helps in detracting potential looters. For example, a larger capacity Gold Storage unit will look empty when a lower level equivalent might look like it's overflowing, despite both holding identical amounts of Gold.
Keep upgrading your Storage units. If they're maxed out, any extra Elixir or Gold obtained from raids will be lost.
When going offline, 'store' Elixir by queuing up troops in your Barracks - choose a high cost unit that takes up the fewest spaces (eg Wall Breaker). Then simply recoup the Elixir by cancelling them when you return to the game. Note that you need to have your Army Camps full first. And don't go raiding before you cancel your queued troops otherwise you'll come back to Army Camps full of the first batch of troops you queued up. This also applies if you're upgrading your Army Camps as any new slots will be filled by the queued troops.
You can't cancel Laboratory research so make sure you're sure before you commit.
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