Main problem lies in the fact that sometimes, even the mission stats after you're finished will say you're elligible for Ghost and / or Clean Hands, although you aren't. I guess whatever they put in the game to do the bridge between Dishonored and Steam for the achievements is not working very well. Or maybe it's just in the game itself.
Yeah, Granny Rags, Slackjaw, I'm talking of you.
Also, it may be possible that "restarting a mission" while on the final stats of the mission count as replaying it from the main menu rather than actually reloading the progress. It's not very clear yet, but if it does indeed work this way, it's lame. One would assume the most logical thing to do when attempting a Ghost playthrough would be to restart the mission when the stats say you're not doing well.
Other than that, having to re-do a mission to get the ghost / no kill is fine by me - just have accurate post-missions stats. We can already check if we killed people ingame by hovering the cursor on the body. If you see "unconscious", it's okay. If you just see the name, ie "Overseer", he is dead and you're not good. Also, no snoring = dead. ( can't remember if the weepers snore, though ).
The detection thing is kinda harder. There are sounds ( I always play without the UI helpers ) but it's hard to distinguish which is which. Best bet would be to check if the guards are running around with the sword in the hand, civils are covering in fear, etc ( detected ) or if they are just walking around, looking at places they wouldn't normally look at, sword in hand ( they think they saw something, but they aren't sure ). I agree though that you haven't always got time to check their status

I so need this. I am trying to do Clean Hands + Shadow but at the end of the Coldridge mission I always have 1 kill which is RIDICULOUS BECAUSE I HAVEN'T KILLED ANYBODY! I need to know where I messed up and remedy this! I've done the mission 6 times and it hasn't worked for me, and I'm really annoyed. Please Arkane, fix this.
The two only "non bugged" way to have one kill I can think of is by leavig the two guards too close to the door you have to blast open with the explosives. Even putting them in the garbage container will kill them, I think. Just stash them in (or on) the opened container near the first door and you should be good to go.
And in the sewers, don't try to hide the guards in the water : that's an immediate drowning.
If you also got a found body, then they probably got eaten by rats and you have to hide the body better than that - they can be in plain sight as long as the rats can't get up to them!