Here's a compilation of tips for beginners who are interested in learning basic principles behind Starcraft. The post is long but you don't need to read every part to get started. Just look at whichever sections are relevant to what you want to learn; e.g. the latter half of the post is mostly just explanation of theory that you may or may not be interested in. As a general caveat, there are exceptions to every rule, so I'm not claiming these are always the right thing to do. They are just good principles to follow absent any compelling reason not to; as you get better, you'll start recognizing when to deviate from certain rules.
Sometimes a gem, is just a gem.