The right play is going to depend on the matchup (if they're a very fast deck it could be right to block), your hand (if your next play is a Ghoulraiser and your creature is instead a Walking Corpse, it is excellent to block), and your tribe along with your deck
Cycling is a nice safety valve, keeping it useful even when the board doesnt cooperate
If the spell has any mandatory additional costs, such as that of Titania, Rugged Rumbler, those must be paid to cast the spell
The most famous of these cards are the charms, like Piracy Charm, though theres plenty of diversity and even mechanics like spree and escalate that build upon this template
This card can be milled and still do its job
Elves have less trouble hitting the number 10 than youd think