You don't mention what your current typing speed is, or what your goal is.
"Much higher" has entirely different connotations to a(n)
secretary administrative assistant than it does to a coder or even a network administrator.
At my best as a coder, I was hitting the 60-70 WPM range, and that was fine. Now that I'm back in network adminning, I've probably dropped to the mid 40's, and that's still plenty fast; I'm the poster boy for poor ergonomics, so if a lazy bum like me can do that, you should have no major difficulties hitting any speed you need, unless it's warp speed like the above-mentioned assistants and data-entry types need.
If you do need that warp speed, then you need to look into the whole ergonomics package: seating position, keyboard and monitor position, copyholder position, the keyboard itself. (I can't hit full speed on a "modern" keyboard, the feel is all wrong. I learned to type on a Selectric typewriter, and so, the only PC keyboards that have ever felt right (and therefore, the only keyboards that I can hit full throttle on) are buckling spring type (old-school AT keyboard, in other words).
Basically, to hit your maximum speed, get comfortable, in terms of seating, hand position, monitor position, keyboard, etc, and then start practicing.
Side note, as far as I know (I haven't looked it up recently to be able to cite), but there haven't been any definitive studies that show Dvorak, QWERTY or any given layout to be demonstrably faster/superior for a properly trained operator than any other layout. Pick the layout you like and learn it.