One of the major changes to the hunting formula introduced in World were Scoutflies, glowing flies that help you track monsters.
The Iceborne beta does help you get going by telling you which area to search for Scoutflies.
Once you arrive to the marked region, look for glowing green flies, which circle above footprints and other marks left by large monsters.
Examine the footprints with the Circle button and then follow the Scoutflies to the next marking.
While hanging onto a monster, press R2 to quickly shoot all Slinger ammo at the monster.
But beware that it eats away at stamina — a lot.