Personal experience has taught me that unless you know what you want, know what will make you happy, and are willing to make the effort, nothing's going to change. Surround yourself with things that make you happy, help you ignore or forget the things that are bringing you down. Don't expect them to be an instant fix, but believe that eventually you'll find laughter and joy in them again.
As already suggested, talking to people (anyone really) can only help, at least if they are genuinely offering to listen. Of course, if you're too uncomfortable with the thought of talking to a stranger, that's fine. Just sometimes it's nice to talk to someone completely removed from the situation. You're more likely to get an honest opinion. I'm not sure if you have brothers or sisters, or parents that you're close to or feel comfortable confiding in, but hopefully you do, and hopefully they'll be supportive. Having people you love and trust beside you for support will help.
Has the insomnia kicked in? That's the worst part, at least for me. I spend the night over-analyzing everything in my life, which only leads to feeling further depressed and alone. If you're having difficulties sleeping, your muscles are sore, you get more headaches more often, or you have less energy than ever before, it may be time to talk to a doctor. I don't like resorting to medication, but sometimes it's the best (and only) step.
Surrounding yourself with supportive family and friends, things you enjoy, and keeping positive is the way through depression. Every time you find yourself focusing on the negative, remind yourself of the positive. Don't feel like you have any? You do. Can't think of any, talk to people, have them point those positives out, and write them down. Negativity only breeds negativity.
Lastly, if you need someone to talk to, someone with experience and knowledge of depression, I'm more than happy to listen. I'm also happy to give you more advice, if you're too uncomfortable telling me personal things. I'm here for support, because I know what it's like, and I don't want someone going through it alone if I can help it.