First, you'll need to find out where and how the PDA holder can be installed in your car or any other vehicle. Check out the picture below to see where I installed my PDA holder.

My Jornada 545 in the DIY PDA Holder in my car

My car happens to have a console rigged with a cassette holder. And if you look closely, you will see that the cassette holder is not 'molded' together with the console. It's actually an add-on. Thus, there is a gap between it and the main console. And where the gap exists, a metal sheet can be slipped inside and attached there. 

I figured that it was the best place to install my PDA holder because no glue or even screws were required. Furthermore, it was right below the el-cheapo cassette player that came with my car. That's exactly where I want it to be because the stereo line jack can then be rigged between both devices to get me an ultra cool MP3 player right in my car!

So, here goes tip number one. Look for tight gaps where a metal sheet can be slipped in snugly and held there. The gap does not necessarily have to be vertical. Any alignment is okay because the metal sheet can be bent anyway. However, if you can't find a suitable place to slip in a metal sheet, don't despair. The keyword here is creativity!

Instead of looking for tight gaps, look instead for clear areas or any side panels. If you don't mind drilling some holes on any part of the console, then go ahead and create a suitable place. You can always use screws to hold the PDA holder to the console.

Okay, now that you found or created a suitable place, let's move on to step two.