If you want to keep the exhaust chrome nice and shiny, as JP says give it a good polish with Solvol Autosol (not cheap but you don't need much it goes along way
) using a fairly hard cloth (old denim jeans are good) work it well in till it goes BLACK keep rubbing till all the polish has dissapeared
Then BUFF it as vigorously as you can [till your arm aches] with a clean DRY soft duster/teeshirt/old cotton knickers till it shines
Then start the engine and and get the pipes/silencers warm {not hot} and turn the engine off
Then, whilst it's still warm take another clean soft cloth and smear the exhaust with 3 in 1 oil and leave it to cool off
When cold you can wipe off any residue and re-buff to leave them sparkling
The exhaust will stay shiny for a lot longer than just a "standard" clean and polish
When its warm the chrome expands and the "pores" open up so the oil gets "absorbed" and helps to repell moisture and the chrome will last a lot longer
Once a week if you ride a lot, once a month if you don't
Enjoy