Hi Lumox
There's an extensive list of tasks doumented on the UK site for you ....
http://www.benefiscal.co.uk/forum/index.php?topic=4659.0At the very least I would:
1.flush the tank to make sure there isn't anything to foul the carbs
2. Put inline fuel filters in the fuel lines
3. Check that the petcocks (fuel taps) don't leak because the seals will probably have gone in the 12 yrs.
4. change the engine oil, the middle gear oil and the final drive oil
5. Buy a new battery
6. spray a little bit of oil down each plug hole to help lube the piston rings at least 24 hours before you even try to turn her over
7. Turn the engine over by hand or foot long before you turn it over on the starter
8. Fit new plugs
10. check all the slides move up and down ok on the carbs before you even try to start her
Peruse that list and you should get a good idea of the tasks that lie ahead. I did 90% of that list and the bike runs like a dream now. It was as rough as guts before I started doing those things.