Look first of all, don't be scared. Dar ko jitna dar manogein, vo utna piche parega.
1st of all, aap Pura Sala pehle apna books khatam Karo, with clearing all doubts. Jo v doubts rehega, chota se chota cheese, pehle uska clear karoon. Line by padho, all solve the whole exercise..
Now, comes to preparation,,, look saal bhar koi preparation nehein karta, preparation start hota hein asal Mein exams k 3-4moths k pehle. Toh Sal bhar apna sab kuch khatam Kar liye, sab doubts v clear karli then usko bar bar likho. Jaha par jo v mock vagera ho, vo sab do. Khudko itna Kabil bana do ki doubts v tumhare pass ane se darein.. Toh Yeh sab tab hoga jab ek chis ko bar bar likhoge, & solve karoge. Then you will find ki ek chis krte karte doorsa kuch v nikal Ata hein..  Aur time badh Kar sab karoon, nehein toh Vele ho jayogein.. Bst of luck for your board exam's..

Don't be scared.
Revise notes and ncert questions, they will help u a lot .