Please read your question again and understand how confusing it is. You ask about how to best prepare to join a startup. Then mention that your family wants you to have a startup job. Then mention your family is putting pressure on you to get a job so they can "come". And then ask about jobs for "freshers" - 4 different points. So, first things first, given your inability to communicate coherently, I wouldn't hire you for any job - startup or other.
I'll just deal with what to do to get a job in a startup:
I am a 25 yr veteran of the tech startup world and now consult to startups. One of the recent trends seems to be recent grads doing startups with little to no work experience. I find this laughable. Startup is a much more challenging work environment than a job you will find in an established company. You will have much less structure, fewer resources, poorer leadership and management, and also will face huge goals and challenges.
Question: Why on earth does someone with no work experience - no less, successful work experience where they were promoted, got raises etc. - think they can jump into a startup and be effective and successful?
Startup failure rates are higher than ever, and i think in part its due to lack of actual work experience and skills on many startup teams (also due to bubble economics driving imbecilic investment strategies by VC/Angels). But even in the best of circumstances, with experienced, talented people (and I'm sorry I can't tell if you are a talented worker by your college transcript, i want to see real work experience), the failure rate is very high. Startup is hard, you should know what your doing, not just have ambition and a desire to 'do a startup'.
My advice? Get a job with a great company that will help you develop your skills and work habits and business knowledge. Gain practical knowledge and also focus on excelling at your work. Get promoted, get raises - these are confirmations that you actually are a good worker. Get a supervisory/management job and be good at it.
Then join a startup that has a good idea, is well capitalized and is run by adults who have a clue as to how to run a business.
As for what to do as a "fresher", which I guess means you are a freshman, well, I suggest you bear down on your studies and master the subjects you are studying.