Again, I still recommend that people wait until clack actually confirms the event and the rules of it before interrupting their life for nothing (you'd have wasted two days already if you started Friday night). If you want to be the person that shows up 11 days in advance to stand in line for a sale though, then, well, that's your decision, but personally I'd rather just miss the first day (and you're guaranteed to miss days if the event is similar to last year [unless you're botting] due to how random the dude is).
Assuming it does happen though and it's the same format as last year- don't refresh the thread, it takes way too long to load (especially once he opens the post to replies, the server pretty much dies). Realistically watching spy is probably the best approach, because it can be 10+ seconds between clack replying and opening it up to replies, by which time it'll have already updated on the spy page. Some people use tapatalk alerts instead, but those have been prone to being delayed (sometimes days). From there, just have the reply page open in a tab already and f5 it until it's open and make your ****post.
Keep in mind that forum is on a different host than the one it was on at this time last year, so it may turn out it's not even capable of supporting the bum rush of traffic a CV event will draw (possibly forcing clack to change up the format). Also be sure to
disable the reply while typing notifications, or you'll pretty much never be successful in getting posts in (assuming old format). You'll need to be more mindful when posting in general after you disable that setting though.