How do I study for Haryana civil services at home?

First and foremost the candidate should be aware of the examination pattern and selection process which are necessary ingredients to begin the self-study. Devise a time table and adhere to it stringently without fail. As in the case of all Civil Services examination, it is a three-stage process like:
i) Preliminary: There are two papers(General Studies and Aptitude Test).Each of the paper is of 100 marks each.
ii) Mains: There are 5 papers namely (English (100marks), Hindi (100marks), General Studies (100marks), Subject 1 and Subject 2 of 150 marks each)
iii) Personality Test: It is face to face interview of the candidate with a panel of the examiners where he is tested for his knowledge of current affairs related to the state and personality based questions.

In order to start preparation for HCS Exam, focus on the state as most likely about 20 questions related to Haryana in General studies paper of prelims. The best book for Aptitude Test is McGraw Hill. it is advised to read the NCERT books from Grade 7-12 to build the foundation followed by reference books on the subject. For English and Hindi, any good grammar book will do. For General Studies, the books read in prelims will also help in mains.
After mains, you will have a Personality Test of 75 marks. Besides, there are online resources which are extremely helpful for the students in their preparation. Some of the leading players in online HCS Exam coaching are Mrunal IAS, Unacademey and Civics Daily.