If it's something similar to what I already use (like say trading one web framework for another), then I just look at the official documentation/examples and so

If it's something similar to what I already use (like say trading one web framework for another), then I just look at the official documentation/examples and some decent guides. After that, I start building something with the new tech. If it's something like a new language or database, then I might be more interested in getting a book on the subject (if there exist any decent ones). I'll usually skim through the book looking for areas that differ significantly from previous languages/databases and focus on reading about those parts. Following that, build something with the language/database. Reading stuff only online if it's not official docs, can really burn you though (not that books can be any better at times, but books at least get reviews). Most of us probably already know that, but the quality of content of many blog posts and tutorials can be sub par (especially for things like PHP and Android). The faster a piece of technology changes and the way one uses it, the higher the variance it seems in quality of online content (just looking at bad practices in PHP from version 5.2 and before to 5.5 and also Android 2.x and before to 4.x). Pretty much though, it all comes down to building. Reading can get you past some of the basics, but applying what you learn reinforces. Also, it doesn't hurt to eventually teach/discuss what you're learning with someone else, as it helps to also reinforce what you already know and question what you are unsure about (either actively or in retrospect).