Don't worry too much about switching after six months at this point. You just graduated and you're finding your place in the world. Explain yourself as you've done here, and don't make it a long-term pattern. The best way not to make it a long-term pattern is to find the kind of company you want to work for, doing work you like and are good at.
As for how to get in somewhere... I had heard that if you really wanted to work somewhere then you should let them know, and also follow up. Once I picked a place that I wanted to work and I applied. They turned me down, saying there were no openings (I just cold applied, not in response to a job listing). Every few weeks I checked back with them. Yes, they hired me. ;-) I only did this once, but that makes my success rate 100%. YMMV.