To prepare for Polytechnic first of all you should be familiar with the syllabus of that examination. Syllabus is almost same for all polytechnic entrance examination, you might download or see from any previous year question Bank.

First of all clear you basic from NCERT of class 9 and 10(Mathematics and science).

After that solve previous year paper of the university for polytechnic you wish to appear.

Previous year question Bank is easily available in any bookstore. Solve it religiously.