Writing Feedback / IELTS Exam; essay part, intro, every related information [2]

Need a help from you people what should i focus on while doing essay part because i m afraid of giving exam..
i m really facing so much problem how my intro should be
is vocabulary is needed good for scoring approx 6.5 Bands ?
please give me each and every information related to this guys
what type of essay it shoud be >
i m waiting for your reply guys