1. Pay attention to everything you can in the work place. You may be a client side developer, backend, whatever, but pay attention in every meeting or conversation that you can eavesdrop on. You may not understand everything going on with the teams you don't work in, but just being exposed to their terminology and _looking up what they're talking about_ will get you far. This doesn't go for just development, either - listen to the business and sales guys talk and try to understand your clients and what they need so you can build a great product by anticipating what will work for them before they have to ask.
2. Write a blog. Seriously. I'm the first to admit that I don't really know anything when it comes to development, but I've been actively writing new posts to my blog and it forces me to grok whatever I'm writing about. Whatever you're doing, post the code on GitHub so others can read it (mine's here). Developers who read peoples code online tend to be awesome about making suggestions and asking questions that make you realize you screwed up without being jackasses about it.
3. If there are tech meetups in your area, go to them. If you're in a decent sized city (I'm in the Denver/Boulder area, which isn't huge, but it's a lot bigger than where I'm originally from) you can find multiple meetup groups related to tech that you're interested in. It's a great way to learn new things and meet a lot of awesome people in your area.
4. If there's hackathons in your area, no matter how small, go to them. You meet awesome people and learn how to work in teams that are different than the one you're in every other day. Plus there's usually free food and beer, so what's not to like about that?
5. Pick up skills that compliment your work area by doing projects that aren't work related. It helps you understand what other teams are doing and how it affects you, plus it just makes you more awesome while keeping down the monotony. As a client side developer, I've been taking a Udacity course on using AppEngine to make backend APIs, and it's been fun.
6. For the love of God, check for null pointers and other kinds of exceptions. You may not catch all of them due to inexperience in spotting them, but that's what senior devs doing code reviews are for. You don't want code going into the wild that crashes, even when data is bad. Getting a call on a Saturday saying something bad is happening is not what you want - the weekends are yours to do whatever you want, not put out fires that could have been avoided.
7. Open source third party libraries are your friend. People way smarter than me have put together some amazing things that we use every day, like Otto and Picasso from Square. Try libraries out in a sample project, and if they will work for what you're doing, give it a shot. If you can make them better in the process, submit a pull request. Like I mentioned earlier, the open source community is awesome and if your pull request isn't up to par, they'll let you know what you can do to fix it.
8. You're going to fail at some things, and it's alright. Fail early, learn what did and didn't work, and try again. Learning from mistakes is how you get better. Along this same line of thought, if you run into a roadblock that you can't figure out yourself via documentation/stepping back and evaluating the problem, StackOverflow is awesome.