Bolzano to Salzburg

Best is a subjective attribute.
If by best you intend fastest, then a private jet or helicopter would fit the description. It wouldn't be the cheapest way though.
If you have a car, it would be cheaper than a private jet, but it would take you over 3 hours using the autostrada and autobahn via Innsbruck.
Without a car, the fastest is the train. One change in Innsbruck required. Total journey time about 4.5 hours.

Thanks Roberto,
Your cracking me up......I'll take the train, you do have patience with of our questions, I'm sure everyone appreciates your help

I for one enjoy Roberto's answers!

To find train schedules, you can look at German Rail: http://reiseauskunft.bahn.de/bin/query.exe/en (often considered the easiest to use, it has schedules for most, but not all, lines in Europe). Here are Rick's tips on using it: http://www.ricksteves.com/travel-tips/transportation/trains/online-schedules

I'm not sure if the Bahn site will have prices or allow booking for that trip. If it doesn't, you'll need Italian Rail http://www.trenitalia.com/ or Austrian Rail: http://www.oebb.at/en/index.jsp

To find driving details, use ViaMichelin: http://www.viamichelin.com/