Hi Brother Adidas88,
Thanks for your reply. Only me & 2 of my friends and usually we quite cheapo....only drink beer...the most 1-2 dozens.
Some questions:
1) How much for a small room for 3 of us.
2) How much for drinks.....assuming 1-2 dozens
Honestly ... i DunNoLah .. 
.. becoz me dun drink and i dun want to know the rate, so my buddies will settle everything and tell me what's my share ...
.. me just enjoy myself with meimei and let them take care of the bills ..
3) How much are gals cost (Sitting-ST-ON)?
Ah ... this one i know very well ...
rate is usually 2-5-8 ... some ktv, like 梦回巴黎 is slightly higher .. 3-6-10 ..
4) Do we have to give tips to Mamasans? If yes, what is the normal rate?
no need to give mummies any tips unless she's damn good to u ...
so far, i have onli gave once to a mummy in ZH ...
I am more concern about the gals attitude coz very likely we are going to take them for ON.
well .. gal attitute depends on ur luck and chemistry ....no sure win formula .. treat them with respect and everything shld be fine
I just hope that I don't kana chopped carrot by them coz we are not familiar with the place.
u can always checked with the KTV managers beforehand and if u r not comfortable with the place, move on to other ...