I will start the process of analyzing the poem, but I have indicated a couple of sites at the bottom that will be able to continue where I stop. Combine my thoughts with the sources and your own understanding of the poem, and you will have all of your questions addressed. The poem is a Scottish Lyrical ballad about a speaker who comes across two crows (corbies) having a discussion about where they shall eat and what they shall do as they spot their target for scavenging: A corpse of a knight. It's interesting to note that "Twa Corbies" is a variation off of an English Nursery Rhyme, "The Three Ravens". In the British version the three ravens holds the same discussion witnessing the same dead body. Yet in the British version, the master's hound protects the body from any ground scavengers, while the hawk protects it from the air, and the doe in the forest cleans and buries the body with the deepest of respect. In the British version, there is a sense of reverence and honor for the slain knight. This is certainly not the case in the Sottish "Twa Corbies", where the dog has left, and the hawk has flown, and the doe has taken "another level." This vision of the slain knight is a rather cruel and desolate view of death. The presentation of the images of death are through the raven's point of view as seeing life as a scavenger. In the fourth stanza, the two birds talk about how they will desecrate the corpse to get what they want from it. Again, because there is a stunning lack of respect for the dead knight, the birds say that they "can mak our dinner sweet." The poet ends with stressing how the body will decay and only the bones will remain. Obviously, the poet is making a statement on death and dying. It seems that human beings, according to the poem, endure two deaths: The first one is the death of the body, and the second one is the death of one's dignity when one does not have anyone to provide care and protection from "the scavengers" that walk amongst us. It is very interesting to contrast the Scottish Ballad with the British version because both give an opposite picture of the view of the dead and the respect for them.
The best way to understand the poem is to make sure you know the Scottish version of death. To analyse the poem or a ballad in technical terms, the anonymous poet is talking about two crows or twa corbies in Scottish, about their discussion on where they should go and dine the following night. They see a freshly murdered knight under a tree and quickly start to talk about how they are going to eat him. The ballad is showing us the mental picture of somebody's death who is an anonymity to the world. In this the knight's hound, hawk, and lady have left him as now he is nothing to them but a past and in the British version, the hound stays and guards his masters body whereas his hawk has gone in search for food and his lady love who once was in love with him has left him for another man. Twa Corbies is a true picture of events about this materialistic yet cruel, rude, and harsh world that forgets those who aren't widely recognized just an entity. It also explains us the pathetic state of the grey shaded world that seems so colourful with the colours of rainbow. What we should focus here on is that to understand this poem one should be familiar with death and life so to grasp the concept behind it. Twa Corbies is one ballad that actually gives you the gruesome state of things that happen in this world to a dead body that people don't pay respect to.
I've seen a few of these interpretations online, and all of them fail to mention something I think is rather important -- the knight was very likely slain by his lady, who then left him to be with her new lover. The second raven (corbie) tells the first that the knight is 'newly slain' -- he didn't die from an accident or any natural causes, he was slain. But only three other beings know where his body lies: his hound, his hawk, and his lady. If anyone should know where the knight's body is, it would be his killer. Since it's unlikely his hound or hawk killed him, that leaves his unfaithful lady, who certainly has a motive to kill him.
This really is the only logical interpretation. Not only does his lady have a motive to kill him, she has a motive to leave his body somewhere it is unlikely to be discovered and properly buried. If she weren't his killer, she'd really have no reason to leave him to such a fate. Also, if she didn't kill him, someone else did, which means there's a fourth being who knows where the knight lies. If the second raven's account of things is to be trusted, this isn't the case. Therefore, the faithless lady must be the knight's killer.
So amid all the imagery of death and desolation, there's a little murder mystery hidden in this poem.
This may be one of the shortest analyses that you'll find but it is certainly the best. The critique, which follows several versions of the ballad, makes cultural comparisons rather than value judgements.