Still learning my way around this hobby - regarding Cx wait-list, what's Best Practice? (it's my first time asking about ANY waitlist)

Do I book my J-ticket now, and waitlist F and hope it shows up? Then what?

Or more applicable to me - a single F is available, a second one is wait-listed...buy two Js? One of each? There's the airlines "official" policy - and then there's what all of you do!

Thoughts? Hints? Overall odds of success?

Thanks everyone, so far, I can't believe I have let this knowledge sneak past me for the last ten years.