You’ll learn about the ～たら form soon if you haven’t yet (sounds like you’ve already learned with ～た). Like Leebo says, it’s primary function is as one of the the three commonly used (and all slightly different in nuance) conditional forms in Japanese. It has a few other uses indicating sequences and expectations, but you’ll learn those probably in intermediate study material.
But yeah, unless it’s 思ったら, there is a good chance when you see that ending that you’re looking at an “if/then” / “when/then” statement.
Nothing to add on ご and お! They’re just respectful prefixes and there’s no real way at them (for your own use; understanding is easy) but memorizing which one tends to be paired with what words.
Edit – Incidentally, you’re looking at one of the other conditional forms at the end of the sentence in the title.