I've noticed that you don't always diagram conditionals. Is there a time when you don't recommend diagramming?
I'd say the best way to think of conditional symbolization is as a tool - really, in pretty much precisely the way you'd think about a hammer.
When you're driving a nail, there's just nothing better for the job than a hammer. I mean, you could do it another way (whacking at it with your tape measure, or with the sharp end of your screwdriver, if you're really precise and awesome with a screwdriver), but for putting a nail in, the hammer is your best bet.
At the same time, however, you don't go running downstairs to your toolbox to fetch your hammer every time you need to push in a thumbtack.
Conditional symbols are like that hammer - you should use them when you find they help you see the relationships, and you should feel fine with not using them if you can decipher the relationship in the passage easily without them.
As to language cues that tell you that you've got a conditional relationship, I'll direct you to this document, which contains all the conditional language in the world* (*probably not, really, but I am updating it every time I come across conditional language that isn't already on it. So, you know…).