Finally done a CI run (well, ready to do Temple, fully loaded for bear, but gotten a bit bored with the game atm)! I feel like a proper gamer now :)
In the end, I think the absolute one single key (if there is one) to XCOM gameplay on Classic (and I should imagine even more strictly so on Impossible) is to only ever clear fog of war with your first move, even when the first move does unveil X-Rays. Which means, as a side-bonus, that you can scoot around a map fairly quickly (and get to that juicy Meld quicker) by going in column and not worrying about cover, so long as no move subsequent to the first unveils anything.
It also means you’ve got to keep an eye on the “Path” arrows when moving soldiers subsequent to the first - having your man move round the side of the truck that might unveil mobs, instead of round the side of the truck your guys have already been, can make all the difference. Even just one square wrong can lead to disaster.
Full cover, elevation and flanking are great when you can utilize them, but they’re chance-based (or rather map-based, but of course once you know a map it’s all much easier anyway); not unveiling fog of war after the first move in a turn is one thing that’s always under your control.
Other than that, it’s the usual thing of managing panic with satellites and judicious use of the Alien Base at the right time, while balancing the need to have the Alien Base up your sleeve with the need to get ready for the first Terror mission and have lasers/decent mec/genetics for that.
What I particularly love about Ironman mode is the way it makes your wee soldiers matter even more, and that side of the game be even more immersive. Finally, even, there’s actually a use for the memorial, and you can shed a tear for your favourite-up-till-then soldier who bought the farm, and the incident is engraved on your memory :)
Next up (when I get a hankering for the game again, as I have no doubt I will) CI with Second Wave options, after that Impossible with saves, then I/I, then I/I with Second Wave, all while trying different tactics and combos of upgrades, etc. Then, I should think, the game will be done and dusted. Great value!