"Ozymandias" by Percy Bysshe Shelley is a frequently taught poem at the secondary level because it is fair simple for most students to read and understand. The first thing you might do is provide some historical background about Shelley, especially his atheism and political radicalism and his attitudes towards nature. This in many ways contextualizes his general approbation of the fall of a great king and the triumph of the desert over the ruler who tried to dominate it.
Next, you might want to discuss the sonnet form, and have students scan the poem. It is very important to talk about metrical variation so that they are actually hearing poetic rhythm rather than just randomly marking five iambs without any actual analysis.
Finally, you might discuss the "sic transit gloria mundi" theme as a way to consider the desire for material power, especially as it is treated in the final lines:
Nothing beside remains. Round the decay
Of that colossal wreck, boundless and bare,
The lone and level sands stretch far away ...