I've been playing guitar for about 2 years and a half now. Most of the time I've been studying blues and rock soloing but I want to get in to metal and shred. Where should I start? Yesterday I bought Rusty Cooley's(One of my favorite guitar players) Shred Manifesto. Will that help? What excercises should I do? Scales?

Thanks in Advanced
learn the 7 modes, pentatonic scales, blues scale, iolean, lydian ect.
most of the rock and blues scales can and are used in metal

Im in the same situation. I've been playing for 2 and a half years and mainly done rock. Now I'm moving onto shred. The main thing you have to do while learning to shred is take it slow.
Im not going to say I'm a good shredder, but from what I've heard from people, I know what can help.

Firstly, ALWAYS use a metronome. Start of using it slow then eventually build your speed up. Perfect practice is better than trying to play fast but sloppy.

You should consider trying the 21 day routine.

This is playing exercises and licks slowly to a metronome for 21 days. It is best to do this strictly though, as in do it every day for 21 days. This is said to help build up speed and is best for accuracy. This is the method I am using at the moment. I will let you know if it works after the 21 days.

You should also learn the well known shred techniques such as:

Alternate Picking
Economy Picking
Sweep Picking
String Skipping

There are great lessons on UG that you can check out to help you. I found them very useful. Also for sweep picking you should the UG Steal This Video. I found this 10 times more helpful than simply reading lessons.

As for exercises you should look at Steve Vai's 10 Hour Guitar Work Out.

I used this and just varied the exercises to suit me. Using these to a metronome is also a must for best accuracy.

Finally, a lot of people will probably say to you that you should search the forum before posting. This is true. There are hundreds of shred topics in this forum. Also you should check out the 80's Rock, Shred & Progressive Forum

Now I hope that helps for now. Any questions then do ask.