Before starting you should ask yourself if you really want to crack this Competitive exam and Why ?
All your questions will be answered in that .
Now what I am suggesting now will come to you on your own –
1 . You should first read the syllabus of your Competitive exam thoroughly and stick to it through out your preparation.
2. Set daily targets ( achievable ones ) and try to achieve them , write down the reason if unable to achieve on any particular day , then try not to repeat that reason .
3. Sit on your chair with table and write whatever you study in your notebook, will help in long term memory.
4. Give sample exams on regular basis to judge your progress and analyse your mistakes every time .
Daily regular study is the key no matter what , you need not be very very intelligent to clear these exams but determined and punctual .
You will have ups and downs but how you manage them will decide your success.
In all minimise your mistakes .
All the best