Remember that you want to approach the text in steps: Observe (collect information: attentive reading); Interpret (give possible meanings to what you observed); Evaluate (how do you think about it, and why?)
We will not list all possible questions here, but we'll give a few pointers.
Observing:
You can start by asking how the narrator feels - pick out words like 'Hungry', 'Wet', 'Muddy': are those sensations nice and pleasurable? What about 'he was thousands of light-years from home', 'the blue sun' or 'the gravity twice what he was used to': what do those evoke? (far way, different and alien environment: uneasy, afraid perhaps, a bit lost).
Draw attention to the aliens; how they are introduced (war at first sight), and described (cold-blood killers, invaders without pity etc,): what type of people (so to speak) do they seem to be? What could they want? And why won't they talk to the narrator's race, since they are the 'only two intelligent races in the galaxy'? Isn't that a waste - isn't that stupid?
You can begin making links between what you observe and the real world - our world, for example by asking about human history: have there been times when a group of people invaded another group's territory without asking? Have there been times when a group of people attacked another group without bothering to talk first? Have there been wars, and what are they usually about? This is what the middle paragraph is about.
Note the last-but-one paragraph, a repeat of the first, to re-build tension in the text. Then of course the last paragraph, where the narrator is revealed to be an alien (respective to us of course), while the human is the alien (respective to the narrator). Note the vocabulary used (ghastly), the sense of revulsion and disgust at a creature without scales and fewer limbs: why that revulsion, that disgust? And how do we usually react to what disgusts us? (fear, aggression, rejection etc.).
2. Interpret:
you have already done some interpreting, by trying to give possible meanings (=explanations linked to the real world) to aspects of the text. Now you should ask interpretive questions: Why do the aliens attack? Why don't they talk to their opponent, why don't they 'even try to communicate'? Why is the narrator defending what he describes as a meaningless planet? And why do the aliens want to take that planet so badly?
Of course, you do not want to ask those questions one after the other, get one answer and move on: these are just some questions you can ask, comparing answers, weighing up options, adding another question to the question asked (follow-up questions), and using the learners' ideas and interpretations to fuel the discussion. Some themes you can touch upon are of course War (why do people sacrifice themselves for their country; why we think it's better to wage it than negociate etc); colonisation (taking someone else's home, destroying their culture).
Obviously, the twist at the end deserves your attention: why does the text end like this? Why do you think the narrator is an alien? This perspective shift can be linked to its function (making us see ourselves in a new light) and its possible interpretations (forcing us to reflect on our history, our ways; forcing us to consider how we treat others how we justified our wars)