Frankfinn Institute of Air Hostess Training.

In general Candidate Profile for Freshers for cabin crew is as under :
Age:Between 18 and 27 years
Minimum Height:Men - 170 cms and Women - 157 cms
Weight:In proportion to height
Educational Qualification:HSC (10 + 2). Candidates who are appearing for their HSC examinations can also apply
Physical features:Pleasing personality, clear complexion (scars, pimples and blemishes not acceptable) and good eyesight
Marital Status:Unmarried
Language skills:Fluency in English and Hindi. Proficiency in a foreign language will be an added advantage. Interactive skills:Excellent communication and good interpersonal skills
Nationality:Indian citizens only
Passport:Must possess a valid Indian passport or should have applied for a passport
Mandatory Documentation :Must possess a Pan Card and Aadhaar Card
So that becomes very clear that it merely requires some grooming to get the job of a cabin crew. They don't demand much from candidates. You should be interpersonal sound and capable to handle people from different cultures. Cabin crew is the face of the airline. Coz they face the passengers for the first time. Frankfinn might be having tie-ups with airlines, which I am genuinely not aware of. But trust me airlines will take your test and only then you shall be considered.

Institutes like Frankfinn give you a basic outline of how to appear for any job interview and how to gain confidence in your moves and be personable.
Being presentable is also what matters a lot to be a cabin crew in any airline. Because this job is a part of hospitality.
To be a cabin crew the most important thing is to be confident, personable and clear in communication. Cabin Crew are face of the airline because they are the once who remain with the passengers for the maximum amount of time. Hence it becomes most important for them to be personable and pleasing in communication and presentation.
In domestic sectors it is helpful to be aware of regional languages of the places where the airline operates. So that they may put you on roster for those flights.
In case of international airline, the most important thing here is the same, to know the language. If you are targeting some international airline then learn some foreign languages apart from English. You may go for French, Thai, German, Chinese or Japanese.
A lot of airlines operate to destinations where such languages are spoken.
PD (Personality Development) Classes can be a good option to prepare before you walk-in for any interview.