The very first post qanon ever made was in the vein of the classic chan troll style, which is to say whatever you want in the hopes that it might get a reaction.
Qanon made his first appearance in a 4chan thread which started with a poster asking a question "Why are all the Fox anchors smiling. CNN MSNBC NBC are freaking out like election night".
Later in that thread a poster commented in reply to that question "Hillary Clinton will be arrested between 7:45 AM - 8:30 AM EST on Monday - the morning on Oct 30, 2017"
Qanon made his first post in reply to the Hillary arrest comment, piggybacking on it and adding new details, saying, "HRC extradition already in motion effective yesterday with several countries in case of cross border run. Passport approved to be flagged effective 10/30 @ 12:01am. Expect massive riots organized in defiance and others fleeing the US to occur. US M’s will conduct the operation while NG activated. Proof check: Locate a NG member and ask if activated for duty 10/30 across most major cities."
This first post is interesting for a number of reasons, one it looks like it was a regular chan thread with lots of shitposters saying whatever they like, qanon literally just piggybacked on a lie that was already posted. But importantly Qanon said people could check if Hillary really was being arrested if they asked members of the national guard if they were activated for duty. The thing that made people take notice was an additional lie, that people could check with members of the national guard.