Open a sealed Magic booster pack, reveal the cards, and put one of them into your hand. (Remove that card from your deck before beginning a new game.)
Booster Tutor has 3 printings, first in Unhinged (2004). It has 2 official rulings.
Legality
commander: not legal
legacy: not legal
vintage: not legal
pauper: not legal
modern: not legal
pioneer: not legal
standard: not legal
brawl: not legal
Rulings
: You can open booster packs that contain cards not legal in the format you’re playing.
: You can use any sealed Magic booster pack, including promo packs. As long as it hasn’t previously been opened and you don’t know the contents beforehand, you’re good.