look in the walkthrough section

and truly depends on the level, if its the popo toung or mountain herb for 1 0r 2 star,
leave the area unless you hae wailing cleaver shin (which is the most powerful thunder
longsword in the game, bu requires G*** materiels)
the 5 star one, use eager cleaver, or if you have kirin thunder tails, the devil slicer,
for high rank, use true devil slicer, for G rank, use wailing cleaver or wailing cleaver
shin
or you can just turtle it with a gunlance, but if you wand the longsword or lance, youll
need a couple of tails

Really its quite simple u need to bring as many flash bombs and traps as u can and try to
hit him in the face but bewatre hitting him in the face pisses him of (u can tell by
watching his front legs if they turn red WATCH OUT) when hes mad its best to evad him
until he calms down when he doas just beat the bloody hell out of him until he dies=)

The easiest way to avoid his rage attacks is to stay to one side of him, preferably a
couple steps back just in case if he spins. His rage attacks are strong and quick, but
they are predictable. Do NOT attack while he is in rage mode, doing this often occurs in
eating potions and him hitting you while you eat. The best weapon to use is a GS and wait
for him to fall or leap forward twice, run directly behind him and charge your GS until
he turns around completly, then release right on his head. If your timing is off you could
be using your potions like crazy. Just to be safe bring combo book 1 and 2, 10 herbs, 10
blue mushrooms and 10 honey, this should give you an extra 10 mega potions. I recomend
using armor that has the earplug ability or quickeater. Hope this helps. Good luck slaying
that beast.

but... u need to know that always to roll on your right side/tigrex' left. why? coz first,
his boulder throwing attack can only be done with his right, and when he charges, the
first step of his right acts as MOI (moments of invincibility)
or for short, it DOES NOT HIT U!!!