Sandra,
Okay, I'm not a biker, so I have no personal experience in this.
First, they are called 'handle bars' for the steering wheel.

Secondly, I would use the side kickstand. That puts the bike over on an angle, and it makes it harder to push off that angle. Of course, if they hit it from the other side, it's not going to help that much.
Park it angled into your parking space, so that it isn't straight in. But, don't park it so far in that you'll get boxed in if the two idiot car drivers decide to park directly next to you.
Get a 'Warlocks' or 'Hell's Angels' club badge for your biker...and pray you don't run into a Warlock or Hell's Angels. Get a sticker that says 'Stop Honking, I'm Reloading!'
Get a Motorcycle alarm that goes off if the bike is touched.
Finally, get a VERY big bat. Don't use your guitar, it's harder to replace.

Gary