The way I do it is to create a BlackBerry library out of the pre-verified jar file, according to these instructions.
. Then install the lib on your BB device, either independently or include it in your app's jad (which would look like "RIM-COD-Module-Dependencies: net_rim_cldc,ksoap2_j2me_core-2.1.2). This would be done by "importing" the ksoap lib into your app, which is accomplished in various ways depending on which dev environment you're using.
I think that's about the only BB-specific stuff you'll need to do; otherwise, just put the original jar in your Java classpath and develop away.