Sequencing land drops and spells is a skill many still lack in mtg in general.
spell sequencing: For one, It took @Smmenen writing an entire book on how to play Gush properly before some people caught on to how good the card is outside of Grow.dec or Gush Storm. (Turns out, Gush was THE blue deck)
On lands: I still see players making the mistake of cracking one for a dual as soon as they play it, (many still think "thinning" your deck is a valid reason) unnecessarily giving away info and opening themselves up to wasteland.
Many times players lose to themselves, making the wrong land drop turn one.