If you're one of those people who are frustrated by how stupid everyone is when you give clear instructions, you may be phrasing the instructions in the form a question. And while some people will know that you aren't really asking a question, that you're making a statement, most people will hear a question. I'll give an example:
If you say, "Why don't you go downtown?" when you really mean to say "Go downtown", you may hear a response back that sounds like an argument, but which in reality is the normal reaction to a question. That is, an answer. Asking someone a question may sound more polite to you, and it is, but if you're giving instructions it just makes things more complicated for the person you're trying to instruct.
I've even heard people try to give instructions like this: "Why don't you, just, uh, go ahead and, go downtown, huh?", which is a very elongated and padded way of telling someone to "go downtown". My experience is that the most timid people with the least experience in giving instructions turn it into a complex maze that needs to be figured out. Unfortunately, if you know someone like this, there's really nothing you can do - because they think that their instructions are clear, when in reality they're creating guessing games. My experience is that these people become very angry and frustrated with people, who "just can't seem to get anything right!"
So focus on yourself, and what you can do. People who want instructions from you really don't want games. Just tell them. Use simple language. People won't resent that. In fact, people will very much appreciate simple and concise instructions.
This is what I recommend that you do: practice giving instructions. Go to a restaurant, smile and tell them exactly what you'd want. If someone wants to know the best store in town, tell them, and tell them where it is. No, don't be rude, but don't make things a guessing game for people. And if you find yourself giving instructions on things that don't concern you, shut up.
As a teacher I found that giving clear and concise instructions instantly made everyone around me much smarter! Funny how that works!