"What was Loki's plan"?
Yup, not a great plan, if you plan to make people kneel before you.
Loki's plan makes no sense. Probably because it wasn't his endgame? Let's see closer.
• The rhetoric isn't his normal rhetoric ("Kneel", "You're born to be ruled", "You crave subjugation", you name it). He doesn't stick to it neither before, nor after New York.
• Condition in which he came to Earth in the first place is as well questionable at least: he trips, he's sweaty, with white lips and shades under his eyes. Loki even struggles at first to hold Hawkeye back as he blocks archer's hand.
• Mental slap from across the Universe from the Other don't as well contribute to the statement that he was completely falling in line. Same as Loki naming himself a messenger to Fury ("I come with glad tidings") instead of I AM A KING, and stating for no reason that "Freedom is life's great lie".
• As much as Tony said that Loki was a diva, Loki never drew any additional attention to his fight with Avengers and most of the time was even out of people's view. He didn't even address them to maybe vote for peaceful surrender.
• As Loki said to Natasha, Barton told him everything.
He knows Widow's backstory (and still somehow falls for her primary method: to play a victim to get abuser to gloat over how petty you are compared to them).
He recognizes Captain America ("The soldier, man out of time") and still doesn't kill him on at least three occasions in Stuttgart;
He knows of Banner's condition (and not a single time evokes doubt in him to reach for Hulk, on contrary even);
And he kills of all people Coulson, because if Natasha and Hill know he's close to Tony and fanboys over Cap, then Hawkeye knew it too.
• Then again, with Thor and Hulk thrown off the Helicarrier, why again didn't Loki shoot engines of "flying fortress"? He just saw that Stark mended the engine. And he left Hawkeye behind, as well as used a sniper not as sniper should be used. What did he achieve by attacking but not finishing the Helicarrier? He lost sniper and informer, and won what? Thor and Hulk being thrown off the craft? Of all the two people who could possibly survive the fall and would be pissed off at him if they did? Yeah, great planning.
• And every time he shoots vehicles or aircrafts, he shoots whatever else but pilot's/driver's place. For a person who tries to make a statement, he killed at most about handful people at the very beginning, the others died of blast SHIELD knew was coming.
• Oh, and for some reason Hawkeye, who knows Fury, shot him not in head but in torso, of all places the one where he knows armour can be? And Selvig building in mechanism to cut off power — just in case if truth on the other side that he was so fascinated about turned out not to be overly friendly? Yeah. And Selvig built a mini Bifrost for that matter, Asgardian technology that Loki, being "master of Magic", i.e. science. would know very well.
Loki's field of expertise, in fact, is military deception
In first Thor alone he's shown to be professional at stealth and military ruses (from his decoy holograms and manipulation to briefly mentioned in deleted scene smoke cover he provided Thor and company with to cover their retreat).
And in "Avengers"?
• They play it like he — being a manipulator — wouldn't know that common threat, one that shows off and leaves casualties behind, is more serious than any doubts/differences team must put aside? Loki goes as far as to say that to piss them all off was his plan.
• Compared to "Thor" and "Thor 2", Loki is suddenly a show-off? He wanted attention, yes, but he never invoked it. He killed Kurse without showing off. He supported team during Jotunheim battle without putting an emphasis on himself. He killed blood father in Odin's bedroom and not in front of whole Asgard. Also Loki for some reason openly lies to Thor twice in the movie: he says he's a king (contradictory to his statement from "Thor" that he never wanted a throne, but wanted to be equal to brother), and he says Thor threw him into abyss, given he knows darn well he let go of the spear himself. Maybe it was a way to tell "If two of three are obvious lies, than third iiiiiiis… a lie?"
The Other supervised Loki's work in Avengers and if he could mentally slap him over distance, then maybe Loki wasn't as willing and rather was coerced? Why supervise him if he's undoubtedly loyal after all?
What does Loki need Midgard for? Because it's Thor's favourite world? Thor should grow up and understand that not everything revolves around him. It simply was a world in which Loki knew Tesseract was (one of Asgardian treasures). And one world that could be sold to Chitauri as petty, since it's not Asgard after all. But one that could fight them off with a little bit of help and assemble.
What for would he do it?
Well, he never sought destruction of Asgard, and Chitauri were interested in one of Odin's greatest treasures, which would have drawn Asgard into this war eventually.
And he at very least didn't want of all people his mother, Queen of Asgard, dead?
Of course, to repay dismissive attitude towards himself.
To have an opportunity to escape from Thanos back to luxurious Asgard?
Again, if looked at as it is, Loki's plan doesn't make a least bit of sense. He wants Earth. Why? He let himself be caught in Stuttgart. But what did he achieve? Assembled Avengers and temporarily broke an engine. How Selvig controlled himself enough to help Avengers? Why was Hulk integral to Loki's plan even? Why not kill off couple Avengers that are not as famous as Stark? Like, Captain, a symbol? Or why not put Hawkeye in charge of Helicarrier — the closest military stronghold? This wouldn't've diminished spectacle of overtaking Earth.