If the clutch is slipping then you'll be able to smell it, worn plate springs will be the first thing to replace, look at the both the plain and friction plates for wear.
Depending on the milage of the bike and how long the clutch has been slipping will determin if the plates will need replacing along with the oil and filter of course, one thing not to forget as you reassemble is the
Stack height it must be correct for the the clutch to work properly.
Its a simple job to do, dont forget the associated parts needed such as new gaskets and some silicone sealant.
EBC do clutch kits and are every bit as good as the OE parts
Lets have some pics
THERE IS ONLY ONE THING THAT IS BETTER THAN RIDING AN OUTFIT...
AND THAT IS RIDING AN OUTFIT IN THE WINTER...THIS IS THE GREATEST..... Andreas a.d.k.G