I have recently been using Trailhead to help me study for an upcoming exam and I have been incredibly impressed with how good it is. I have already posted about the Trailhead modules that cover new material, such as Lightning, but what I was surprised about was how useful it was for reviewing material that I thought I already knew pretty well.
Trailhead is definitely not exhaustive in it’s coverage, but what I like most about the modules is that they go over just the stuff you really need to know. And most importantly, they go over best practices. There are so many examples of inefficient and just plain bad code out there (even on some of the Salesforce sites I hate to say). The text and challenges in the Trailhead modules were well thought out and it is obvious they put a lot of time into developing them. It still 
surprises me that something this good is free, but fortunately for us, it is.
If you are preparing for one of the Certified Developer tracks, you really need to check out the Developer Trail. It covers a lot of what goes into the exams and the progressively harder challenges really solidify what you just learned. Unlike tutorials that you can just follow in your sleep, the challenges tell you to do something, but not how to do it. And, if you do not do it exactly right, you do not get the points. You actually have to THINK about what you are doing and this is absolutely the best way to learn.
And if you are a certified developer who has been doing this for several years, there is still stuff for you to learn, even when it comes to best practices. As we all know, this platform is changing constantly and that means that so are best practices.
And honestly, it is just fun seeing yourself rack up the points. I really like the WooHoo I get at the end of the challenge. I am proud to say I have 5 badges and over 12,000 points so far (with more to come). How many will you get?
