A. You have completed 11th from a school under the Punjab State board and now want to change to a CBSE school. It would be possible but the problem is
1.to have a valid genuine reason, transfer of parents, shift of residence etc.
2.The admissions are decided by the Chairman of the CBSE board and it is at the discretion of the CBSE authority, so you can try but keep options open.
B.Please refer to the cbse admission rules on page 14 of this pdf file(http://www.cbse.nic.in/Byelawsenglish.pdf).
C. You need to have a Transfer Certificate in the prescribed format ( the CBSE school that you intend to join can help you), signed by the principal.
The above are important for the process of transfer. You need to look of the good CBSE schools in the area of your choice and the contact the admissions office of the CBSE school that you intend to join.
Once you have the prescribed form the you need the relavant ID proof, date of birth proof, the Maarks sheet of the XI passing and the percentage.
Lastly, a word of caution, many students who have been in state board all along find it difficult to cope when they switch over to CBSE. Think, discuss with your family and then arrive at a decision. You can check the syllabus that you would be studying in XII CBSE to get an idea. Since you say you are brilliant, who may adjust to it quickly in a couple of months.