The price to watch the Quins depend on where you sit, behind the posts cost around £25 while on the half way line it can cost up to around £40.
I would always buy tickets before the games and for the big games you would need to do this at least a couple of weeks before as they can sell out quick.
Getting there is quite easy from the central of London, regular trains from Waterloo will take around 30 mins depending on if you get a fast or slow service, to get to Twickenham and from there it is only a 10 min walk.
The next home premiership match is against London Irish on Oct 31st so check out the tickets. I'm a quins fan and go quite a bit and it is always brilliant fun.