Having been in the industry for over 12 years, I know that it's constantly a challenge to keep up with the latest design trends. Here are a few resources, tips and tricks that I'd like to share, that have helped me stay ahead of the curve.
1. Follow Design Agencies on Social Media
By simply following well-known agencies, it's easy to see what the latest trends are. Read their blogs, check out portfolios of their designers to see what they've worked on recently, and check in on their latest work. Be sure to follow big-name agencies, typically they have the capital to hire the best and brightest designers who know what they're doing. Most of them will post to their social media accounts when they wrap up a big project or launch a new campaign. Look for similarities among their designs and compare them with other agencies— you'll be sure to come across how all the "cool kids" are designing.
2. Read Popular Design Blogs
It may seem obvious, but by keeping up with the design blogs out there (SmashingMag, CreativeBloq, CommArts, AIGA, 99designs, etc) you're likely to stumble upon what things are looking like in the design world. Check out their rankings for best websites, too.
3. Parouse and/or join Behance.net
If you've never heard of Behance, it's a great place to see what's new and trendy. It's a place where young, up-and-coming designers post their latest work and seek feedback. With well over 1 million members, you're sure to come across lots of cool and interesting stuff, not to mention critique of that stuff, which is a great learning tool.
4. Visit Commercial and Big Name Company Websites
Typically, large companies, especially tech companies like Google, Microsoft, Apple, Twitter, Reddit, Facebook will be using the latest and greatest design looks, paired with super-cool technology. Again, these types of companies have the big bucks to spend on design and attract the best and brightest in the industry. B2B companies may be slightly behind in design trends and are usually more conservative, but consumer product companies (Think Nike, Pepsi, Samsung, any automotive company, etc) will be hip to today's jive.
5. Google it!
Simply Googling "2015 Graphic/Web design trends" returns a whole bunch of useful results. Just be sure to sift through old entries and look for articles written within the past year.