Oracle OFA, Tablespaces and Redo Logs?

[Hari Om]

Hi Gurus,

I was reading Oracle DBA Handbook and read article about OFA - Optimal
Flexible Architecutre and it showed what are the different tablespaces
used in any db. These are: SYSTEM, UNDOTBLSP, TEMP, INDX, TOOLS,
USERS, DATA.

Q1) What should be the approximate size for each tablespace....? How
many MIN/MAX Extents should I need to allocate....?

Q2) What would be the difference between DATA Tablespace and USERS
Tablepsace?
I was reading Oracle DBA Handbook- Kevin Loney and have some
questions on it:
In one of the section (Chapter 4 - Section - Online Redo Log Files) it
says: "DBA's need to make sure that the online redo log files are
mirrored by some means" and I totally agree with that. It means (if I
am right) if my Redo Log Group has 3 files then these files should be
on different disks.

However, later on in the same chapter (Chapter 4, Section Third
Iteration) the book says:"The online redo logs should be placed
together on the same disks" do'nt you think it is contrary to the
above statement - isin't it misleading....? Kindly clarify orcorrect
me!

Thanks!