To get the lwjgl runtime into your path while running from Netbeans and in general be able to run and debug in the NB IDE, look in the properties of the NB project, find the "Run" category and add the following to the fields there:
Main Class: net.minecraft.launchwrapper.Launch
Arguments: --version 1.6 --tweakClass cpw.mods.fml.common.launcher.FMLTweaker
VM Options: -Xincgc -Xmx1024M -Xms1024M -Djava.library.path="<Full path to the Forge directory on your computer>\mcp\jars\versions\1.6.2\1.6.2-natives"
If you havent already done it, you probably also need to tweek the Netbeans project.properties file to set the build directory. In the nbproject\project.properties file, you will need to set:
build.dir=mcp/bin
build.classes.dir=${build.dir}/minecraft