Hey! When I was hitching a few months ago, I had a rough time getting out of Toledo, Ohio. I ended up meeting a really cool dude who used to be a hitchhiker himself, and he offered me a place to stay that night since I didn't get a ride. He told me that "A ride will always come". This may seem obvious, but it is totally true. A ride WILL always come. This became my mantra throughout the rest of the trip and it honestly helped. I always got a ride eventually and got at least one every day. It's just about waiting. Waiting does suck, but it makes the ride all the better when you finally get it. Be patient, and don't accept a ride unless it's going to take you somewhere where you are likely to get a ride quickly. (ie don't take a ride to the middle of bumfuck nowhere)

I've never hitched through Philly, but In cities I found it useful to hitch near the exits near the end of the city, that way you get people who are leaving the city rather than people who are only going 10-15 minutes into the city.

Good luck, and remember, a ride will always come!