Car tuning is a great way to modify looks and performance of a vehicle. But it can blow off huge amount of money if not done correctly and drinks lot of fuel. Similar think happened with my Toyota Corolla Tuning, so I will advise you to go with a reliable and experienced Toyota tuning companies. The things which can be tuned are :

Engine Tuning - this is replacing the original engine components with after-market versions promising increased performance output. This is the main thing which should be avoided or performed very well.

Suspension Tuning - This involves modifying swaybars, shock absorbers, springs and other such components of a vehicle. A lowered look can be achieved with shorter springs which will also lower center of gravity. Stiff sway bars reduce vehicle roll during swift turns and improves the grif of inner tires on the road surface - thus imrpvoes handling of car.

Body Tuning - This involves modifying body spoilers and body kit. It is mostly done for improving the aesthetics of a car with various artworks and lightnings. Also includes flushing which involves removing bumpers, key locks, door handles, emblems etc. People even go with door modification - Lambo or suicide door openings are common.

Some companies offer limited special editions which are company tuned - for e.g. the very famous Toyota Supra which comes with modified exhaust system, suspensions and turbo settings. Toyota Avensis Tuning is also very common as it is one of top selling car of Toyota.

Also, before tuning a car, take into consideration your local rules and company warranty policies.

Now look at this excellent video on car tuning