This is a just brief outline of expedition vehicle preparation; there are several good books out there which cover all aspects of getting a vehicle ready for a trip. A good starting point is Chris Scott's "Sahara Overland" and for more detail, Tom Shepherd's "Vehicle-Dependant Expedition Guide"

Priorities

Reliability - Whatever your vehicle, reliability is essential - in the desert your vehicle is your lifeline. Less dramatically, you don't want your holiday in Europe spoilt by a preventable breakdown. Ensure your vehicle is thoroughly serviced before the trip. Ideally, at least a couple of weeks before, so that any identified faults can be rectified. Make sure whoever services your vehicle understands where you're intending to go.

Tyres - Make sure your tyres are up to the job. Quality all-terrain tyres are a good choice and will cope well with all of the terrain you're likely to encounter. BF Goodrich A/Ts are popular and have good characteristics.

Everything Else

As long as you've covered the basics, you don't need to spend a fortune on preparing your vehicle. However, you can make yourself a lot more comfortable and you'll enjoy the journey more if your vehicle set-up is efficient. Easy to use storage systems will keep your vehicle well-organised and you'll spend less time searching the back of your car for bits of gear. Fridges and cooking facilities provide creature comforts, making it easier to have a quick cup of tea or a proper meal at the end of a day's drive.
Take a look at the links page for more information on vehicle preparation and expedition equipment. You'll only find quality companies offering top class service and products.