First things First the prospective candidates should understand the Exam Pattern and the Syllabus. Also, we recommend you going through the previous years question papers to understand the important topics that are repeatedly asked.
The pattern of HPAS Prelims along with the Duration Max Marks and Number of Questions asked is as follows:

1 Paper 1: General Studies
Time : 2 Hours | Max Marks : 200 | Questions: 100

Syllabus:
a)HISTORY
-Prehistoric India, Historic India, Indus Valley Civilization, Vedic India, Mahajanapadas, Mauryan Period, Gupta Period etc
-The Classical Age, Pala Empire, Rashtrakuta Empire, Islam in India, Delhi Sultanate, Vijayanagara Empire, Guru Nanak, Mughals, Arrival of Europeans etc
-Visual Arts (Paintings, Architecture, Sculpture), Performing Arts (Music, Dance, Drama etc), Religions (Buddhism, Jainism, Hinduism, Islam, Sikhism, Zoroastrianism), Society etc.
-1st War of Independence, Formation of Indian National Congress, Moderates and Extremists, Muslim League, Gandhian Phase, Non-Co-operation Movement, Civil Disobedience Movement, Quit India Movement, Cripps Mission, Cabinet Mission, Mount Batten Plan, Partition of India Indian Constitution etc.
In spite of the questions varying each year the Modern History dominates in this section.

b)INDIAN POLITY AND INTERNATIONAL RELATIONS

-Constitution, History, Features, Preamble of the Constitution, Union &Territory, Citizenship, Fundamental Rights, Directive Principles, Fundamental Duties, President, Vice-president, Prime Minister, Parliament, Supreme Court, Governor, Chief Minister, State Legislature, High Court, Subordinate Courts, Federal System, Centre-State Relations, Inter-State Relations, Scheduled and Tribal Areas, Panchayati Raj, Urban Local Governments, Emergency Provisions, Special Status of J& K, Election Commission, UPSC, Finance Commission, CAG of India, AG&SG of India, Subjects of Union, State and Concurrent Lists, Precedence Oaths, Definitions under the Constitution, Constitutional Amendments etc

-International Relations questions are asked from Current events.
In this section majority of questions are from Indian Polity

c)GEOGRAPHY
The Geography section is divided into three sub-sections which are Physical Geography, Economic Geography and Social Geography.
i)Physical Georgraphy
-Physio-graphic divisions, Drainage, Climate, Vegetation, Natural Resources etc.
– Topics related to environment like Wild-life, Soil, Flora etc should be given stress too.
ii) Economic and Social Geography related aspects of Indian Geography should be studied in parallel to Physical Geography.

d) INDIAN ECONOMY
Indian Economy topics like issues relating to planning, mobilization of resources, growth, development and employment, Government Budgeting, cropping patterns, Public Distribution System, Technology missions, Food processing, Land reforms, Liberalization, Infrastructure and Investment models.Social welfare Schemes etc

e)SCIENCE
i)Physics: Questions on Theories
ii)Chemistry: Questions on metal, non-metals, and Organic Chemistry or products
iii)Biology: Questions are asked on DNA, body parts, Diseases etc,
iv)Computer
v) Discoveries, Space and Defence
There could be questions asked from diverse topics such as :
-Ecosystem, Keystone species, Niche, Food chain, Food web etc.
-Biodiversity related aspects: Heavy areas like flora and fauna, endangered species, wildlife parks, sanctuaries, bio-diversity hot-spots, biosphere reserves, IUCN, summits etc.
– Climate change/Environment degradation related aspects: Global warming, ozone hole depletion, acid rain etc. Also note down important points, when you hear news related to conventions or protocols like Ramsar Convention, Montreal Protocol, Kyoto Protocol etc.

f) Himachal Pradesh
-History of Himachal Pradesh
-Geography of Himachal Pradesh
-Administrative & Political History of Himachal Pradesh
-Art, Culture, Customs & Manners of Himachal
-Environment & Biodiversity of Himachal
-Social and Economic Development of Himachal Pradesh
-Current Affairs of Himachal Pradesh
For the preparation of General Awareness of HP purchase one book of History Preparation