I am new to miles hacking. Any "must knows" that I should take note of?

Mileslion is your website to book mark.

He shared a link :- https://milelion.com/2019/10/21/why-cant-i-just...

its one link that opened my eyes (after i met him at a seedly event for mile lion)

I thinks pretty obvious that Aaron has the best summary here.

However, only point I would like to add is, Keep track of miles which have expiry on the card - you dont want to do all the efforts and let the miles expire for no reason

Read the T&C, take note of the exclusions. Do up an excel sheet of the miles card you have, and what category will you use it for, their current promos and mpd. That way you wouldn't be too lost to figure out which card to use. Only spend when you need to, i.e time your card with big purchases.

Never spend more than you should- the miles reward should be tailored to your expenses not the other way around

Always utilise the sign up prmotion for airmiles first. Examples are like Krisflyer Amex card.

Do take note some credit cards have expiry to their airmiles rewards