Introduction:
The UPSC Prelims examination is a highly competitive exam that tests the candidates' knowledge in various subjects, including geography. It is important for candidates to be familiar with certain maps and diagrams to effectively answer questions related to geography in the exam.

Maps and Diagrams to be Familiar with:

World Map:
- Candidates should have a good understanding of the world map, including continents, oceans, major countries, and important geographical features like mountain ranges, rivers, and deserts. This knowledge will help in answering questions related to world geography.

India Map:
- Familiarity with the map of India is crucial for answering questions related to the country's geography. Candidates should be aware of the location of states, union territories, major rivers, mountain ranges, national parks, and important cities. This knowledge will help in answering questions related to India's physical geography, political geography, and important geographical features.

Indian Political Map:
- Candidates should be familiar with the political map of India, which includes the boundaries of states and union territories. This knowledge will help in answering questions related to the political geography of India, such as the location of state capitals, union territories, and neighboring countries.

Climate and Vegetation Zones Map:
- Understanding the map depicting climate and vegetation zones is important for answering questions related to climatology and ecology. Candidates should be aware of the different climatic zones in India and the vegetation types associated with them. This knowledge will help in answering questions related to the distribution of flora and fauna in different regions of the country.

India's National Highways Map:
- Familiarity with the map depicting India's national highways is important for answering questions related to transportation and connectivity. Candidates should be aware of the major national highways and their routes, which will help in answering questions related to transportation infrastructure in the country.

Conclusion:
Being familiar with these maps and diagrams will provide candidates with a better understanding of the geographical aspects of the UPSC Prelims examination. It is advisable to study and revise these maps regularly to enhance geographical knowledge and improve the chances of scoring well in the exam.