Have a heavy learn 'shredder rocket' and 'heat ammo'...
Hit the sectopod with the shredder rocket, so it takes more damage from hits over the next few turns.
Then have the heavy with 'heat ammo', which allows it do double the damage to robots, attack it.
Furthermore, if your heavy has 'bullet storm', then he can fire at the sectopod twice.
gaming.stackexchange.com/users/34276/Callum Walker
My strategy was: Snipers.
Snipers Everywhere.
Basically I had a max rank sniper with a laser sniper rifle and a mid rank sniper with the regular rifle when I first encountered the sectopod.
They both have the Squad Sight perk
so I basically put one guy up close enough to see it and then threw some smoke on him and had the two snipers shoot the damn thing to death.
When I actually started fighting it, the sectopod was the only thing in the area (It did have the drones and two elite mutons but I retreated back so I could unload on it when it appeared, I later found out what you mean by nasty AoE)
One sniper had Double Tap (The laser one) and I basically just dropped it's health from full to about 1/4 quarter left by having my entire squad focus it while it could only shoot the guy in full cover in smoke.
This may have been a one off thing though since it was on an overseer crash where there was a high vantage point for the entire area I parked my sniper at.
gaming.stackexchange.com/users/26319/Shykin
It seems like not many people think about this: Sniper with disabling shot, disable its weapon.
Charge your assault(s) forward and blast it (with rapid fire, if possible).
Only do this if there are no other enemies around
Have support kill off any drones that may be lingering.
Heavy do the same if any drones are left, or just hit the sectoid more.
gaming.stackexchange.com/users/122737/Babap
A heavy with HEAT ammo works well, especially if cloaked (100% critical hit chance).
I just took one out with one shot with just my regular heavy plasma.
Granted, I think that's the maximum damage (30), so I probably got a bit lucky, but even if it does a bit less than that, another solider should be able to finish it off.
gaming.stackexchange.com/users/36420/John
Nobody here mentioned suppression yet, which is IMO very useful when fighting sectopods.
If you can't kill the sectopod within one turn, suppress it with a support or a heavy (better with the support so that the heavy can do some damage); if you can afford it, use two soldiers for suppression.
Everyone else fires.
Should the sectopod decide to use its AoE attack, retreat.
gaming.stackexchange.com/users/165291/Martin von Wittich
Colonel Assault with full Right-side promotions, ghost armor and an alloy cannon.
Cloak, Run & Gun, move next to Sectopod and unleash rapid fire.
Both shots are near 100% hit and 100% critical, with bonuses to crit damage due to Bring 'Em on (leave the drones until afterwards) and Killer Instinct.
This will destroy the beast in 1 move and if you cloaked before spotting it, then it doesn't even know what hit it.
I did exactly this the first time I ever encountered a Sectopod (Classic diff) and wondered what the fuss was about!
I destroyed a drone with my next soldier and hacked the 2nd for a free flying expendable scout.
I realised at that point that I had won the game; nothing can compete with Ghost armor and a Soldier that can kill ANYTHING in 1 move...
gaming.stackexchange.com/users/52343/Dingus
I spotted one in a mission where I had a Squad of Assaults and Supports.. trying to level them!
No heavy along and only one Sniper whom did little but spot the thing.
My sniper baby sat it conceals while my assaults and supports moved around it to flank it.. dropped smoke in then have everyone used the smoke to move in and open up on it killing it in a round or 2
gaming.stackexchange.com/users/109735/Calibre
I just ran into my first sectopod map today and it utterly destroyed me.  From what I can tell, it had a long range aoe attack and a super deadly beam cannon.  The little drones hovering around it and repairing doesn't help either.  What are its attack patterns and what is the best way to take one out?  Does it take multiple turns to charge up an attack?  What are its weaknesses?
What is the best way to take out a sectopod?
gaming.stackexchange.com
<xcom-enemy-unknown>
gaming.stackexchange.com/questions/87407
gaming.stackexchange.com/users/3917/l I
Try a sniper with a disabling shot. Have a shredder rocket and heat ammo. While the most common tactic, to beat sectopod, is using heavy unit, other players found usefull to attack with snipers or a combination of light units.
The community is proposing few tactics that work.