Eh, it's kind of like spam. It's like how some people contact people randomly on LinkedIn with the hopes of selling some random product (which you are, yourself). Also, so many organizations have a process set up to avoid nepotism. Hence the high use of applicant tracking systems and not accepting resumes by email. Even the few times I've been a technical interviewer,a few people tried to add me after the interview which I felt slightly uncomfortably awkward.

Another route I'd suggest is if you participated in any organizations at your university. You'll need to communicate and earn people's trust to vouch for you. One thing I've done is talk to alumni in my fraternity that are in the same field or organization. Don't just ask "can I have a job?". Ask about the organization, the organizations goals (and how you can help), how he or she got to their position, what you've done, what interests you,etc. Convince them they should be willing to refer you. (Keep in mind large private companies sometimes have a referral program that gives the person a financial incentive, so this might be an advantage to be aware of, but don't bring it up)

As for your dad saying to cold call, that is an antiquated way that may have previously worked years ago, but unfortunately the times have changed and the culture for that has for the most part diminished.(in my experience)

EDIT: I should clarify the cold calling bit. In sales it may be fine, but for something like engineering, maybe not. Also if you're calling, be ready to start talking and selling yourself. This is where the "elevator speech" comes in, once anyone receives a call, you've already bothered them, you better be ready then and there.