Sometimes, doing the same thing over and over again might get you bored easily. A job is very much a routine and there are possibilities for you to get bored of it either for lack of satisfaction or rewards.
A career shift might be a big step to take as you would be treated as a fresher discounting your experience in another area of expertise. But when you choose happiness over routine, it takes a leap of faith and love for adventure to accept whatever it takes to face the transition. Here are some tips for you to keep in mind when changing:
Ask yourself why you want to change the job and what kind of change would make you happy. If you love travelling, take up journalism. If you love maths, become an accountant.
You might not be able to become an astranaut from a cartoonist, but you can surely become someone else with the qualification and talent that you possess. So jot down the professions that suit your qualification.

If there is a profession that you really love, but do not fit into the eligibility criteria, check out the exams that can get you a ticket to secure the position and study for it. If you are an engineering graduate but do not want to become an engineer, instead serve your country, you can attempt to get into civil services by taking up UPSC exams or enrol in the army.
Pick out your cup of tea from the list of ideas and research about it. Check both the pros and cons to get a rough idea of what the jobs you like might be. A media job might look glamorous on the outside, but only when you thoroughly analyse on the nature of job, you might learn the long working hours and high pressure that needs to be handled.
Ask the experts. It is important that you find people who have already taken the path that you want to take, when it is something very new. Search for experts from your acquaintances or google about them. Ask a techie, which platform does good in a software. Java might not do as good as C program or mobile computing might do better than network security.
If it is someone that you don't know, send them an e-mail. Don't forget to make it friendly, humble and appealing enough for a stranger to reply back.
Read the newspapers for relevant news about your job. If you want to become a chemist, read about the new chemicals discovered or a scientist's interview. Update your knowledge on the specific subject and make yourself confident of working in that field.