If you are in class 12th or below then You can appear for NDA exam which is held twice a year in the month of April and September and You can fill Airforce as You preference. Students who clear NDA and join Airforce they are posted in service as a commissioned officer.

NDA consists of two parts, after completing written exam you need to qualify SSB interview. Syllabus for NDA exam includes Mathematics and General Ability test.

If you are in graduation then You have three option one is through CDS which is similar to NDA. But SSB part is much tougher than NDA. apart from CDS you can appear for AFCAT in which you will be able to join service under short service commission, In which you can serve for maximum 14 years which will not be extended. There is also University direct entry scheme.