As far as the ISTQB experience is concerned, I just wanted to tell few facts here
(1) No need to join a training institute for preparation.
(2) Read thoroughly ISTQB rex black book and if you face any confusion during reading then resolve it immediately rather then putting on future task o/w it will create confusion during giving examination.
(3) Time is more than sufficient in this exam so you dont need to worry about that.
(4) Exam is very much confusing so read question first thoroughly and understand the context first then give the answers of any questions.