Umm, you want tips on how to make a Suzuki Cruiser faster...from a Kawasaki Sportsbike forum?
I'm going to put this out there but this may be the wrong place to ask.
If he's after generic advice then you could do the following:
* Shed weight - look at lighter bits to replace all that chrome...but this is why people buy cruisers.
* Suspension - look at getting the stock shockers revalved/replaced with more up-spec internals...but you're always going to have a heavy 265kg pig of a bike.
* Braking - look at braided lines...but you'll always have the rear drum.
* Fuel Injection - Look at remapping and/or a PCIII plus tuning on a dyno...but you have a 800cc v-twin that weighs 265kg, so you won't have a lot to play with.
* Tyres - Look at tyres that give more grip...although you're always going to have limited ground clearance.
Note that increasing the performance is going to adversely affect fuel economy and heavy V-Twins aren't that good to start with.
Personally I'd recommend that they trade the M50 in on a ZX-6R or a GSX-R750, and if they'd prefer comfort then a Z750/Z1000 or SV650/1000.
FWIW in my opinion the M50's design brief is not about going fast, it's more aimed at a female/short-arse/newbie Ulyssian with a bad back who wants a reliable Harley clone (male members would buy the C90 bigger engine, more chrome).
HTH, Mick