what is the best way to set it up the truss rod?A bit of relief or straight? for playing fast and shredding is it better to have it flat?? and what are the advantages and disadvantages? thank
A tiny bit of relief is best. This is because when a string vibrates the vibration is widest at the centre of the string and therefore it needs a bit more room to move at around the centre of the neck.
Basically, your perfect Truss Rod position is LEFT THE **** ALONE.

Because, hey, it's not as if it's the main structural stabiliser of your neck.

No, wait, it is.

So you **** with the truss rod... You can **** your neck, beyond repair.
OK, I shall explain the truss rod once more...

1. Capo the 17th fret, and use your hand to capo the first fret.
2. Stick a playing card in the middle of the neck; You should have only a little bit of room. Enough for the card to move freely, but not greatly.
3. Adjust the Truss Rod very slightly to get about 1-2 mm in height here.

That's about it. If you are unsure about your skills in messing with things, take the guitar in somewhere.
- FJ

Quote by Landover Baptist Church
If you find [balloons in his bedroom], it is a sign that Satan may have taken your child by the hand and skipped off together to see the movie, Up without your knowledge.

God... you only capo the 1st fret and fret the 16th or 17th fret with your hand. You dont need a capo actually, you just need to fret the 1st fret and where the neck meets the body, 16th or 17th. See the 8th fretwire, there should be a clearance of 0.3-0.5mm between it and the string. If you string is lying on the fretboard you dont have any neck relief. If its more than 0.5mm than you have too much neck relief. Clockwise will loosen the truss rod and anti-clockwise will tighten it. Loosening it will make it bow more.

For guitars that have 2 studs for raising action, you only need to check the 1st and 6th string, low E and high e only. If you're doing this for all strings, then you're checking for a twisted neck.
"Play with your ears" - Yngwie Malmsteen, Paul Gilbert
Thats what she said...