Read more into things than you need to given the opportunity.

Let's say you need an icon for something, but don't know much about design. Once in a while, try making it on your own. Learn about the pen tool, image formats, etc.

Let's say you need a simple SELECT from MySQL. Read more into how they actually work under the covers, in large-scale environments, or how they change for MSSQL / Postgres.

Let's say you need a particular jQuery function.. take a few minutes to read the source and see what it's actually doing.

If you take a few minutes each time you do something unfamiliar, you'll gradually build up a better understanding and larger skillset without having to put in too much effort.