With my first employer when I started my carrier in performance testing, there were many experienced people who guided me and mentored me. There enough infra structure and necessary applications were there to learn the things. I had chances to see benefits of performance engineering on an application which was suffering previously with performance problems in live. Learning basics under such a high standard was a gift for me. But all our friends in this industry do not get such a luxury :) (being paid for learning under high standard).
But nowadays more people are writing / blogging about performance testing / performance engineering. So the only thing that newbies have to do is, search in net and follow one guide till he/she learns the basics. Later he/she can compare the other approaches and shape his/her approach in a better way.
The following are few links in my Bookmarks.
Articles and Presentations by Scott Barber
http://www.perftestplus.com/resources.htm
Alexander Podelko's personal site about performance engineering and related subjects
http://www.alexanderpodelko.com/PerfTesting.html
'Performance Testing Guidance for Web Applications!' guide by J.D. Meier, Carlos Farre, Prashant Bansode, Scott Barber, Dennis Rea
http://www.codeplex.com/PerfTestingGuide
Forum on Performance and load testing, where we can get suggestions from many experts
Performance and Loadtesting forum
List of open source performance testing tools
