Ask HN: Any good advice for a new grad to join a startup?

I am a new grad from Purdue University majoring in Computer Engineering. In this major we have been taught a lower level perspective of computer systems; a bit of digital electrical engineering and software engineering mostly in C. I made mistakes on my previous 4 years where I have only been giving myself to solve algorithm challenge problems on the web instead of doing real projects as I thought that it was more effective to score an interview.

I had no experiences with higher level programming such as frameworks, libraries and those technology abbreviations (ASP.net, RoR, Scala, etc). I learnt myself and from elective classes about Java, Qt on C++, Python, and C# even though I still do not feel they are strong enough for a job yet.

I would really love to join a software startup as I find it much more exciting and giving invaluable experiences. It doesn't matter if I work as an intern or a full time, as long as I can contribute.

I already found some of the exciting companies that really attracts me and I got phone interviews (I am still at Purdue and most of them are at the coasts area) from some of them. Each of them turned me down after some step(s) without giving me specific feedbacks :(.

I was wondering if fellows HNers have advices for a newbie like me on how to join a startup and really contributes.

Thank you.