If you could only have four planes, which would they be? What brand?
Where would I go to find the best information in tuning and using them
(besides here)?

My first response is the usual "if you could only have 4, which 20
would you pick" since planes are like eating crackerjack, the more you
have the more you want. But it is a good question. I think the
answer depends on how you intend to use them - are you heading towards
being a neander (mainly depending on hand tools), or as a complement
to machine woodworking - or something else such as boat building (I do
a lot of work on small boats).

The advice about the first plane being a low angle block plane is
excellent - I like the older Stanley 60 1/2 block plane with the
nickel plated cap - but be careful because it is important that the
adjuctable mouth work properly. I have found a lot of these where
someone has buggered up the adjustable insert (using a wire wheel,
swaping parts, etc.) and it is impossible to get the sole flat. The
ones with the knuckle joint cap are nice too - and the older Craftsman
and Millers Falls planes can be just fine. I must have a dozen of
these now, and favorites change from time to time, but this is the
essential plane.

Since I work on small boats a lot, I am very fond of the No. 3 - it is
really handy for getting out planks, etc., and just a useful all round
plane. If you have kids in the shop they really like this plane too.
But if you are more conventional woodworking I think a 4 or 4 1/2 is a
better choice - the wartime 4 1/2 with the plastic adjusting knob is
the heaviest of the lot, and can be tuned to be a wonderful smoothing
plane.

And the 5 - or even 6 Stanley seems to be the favorite plane for
getting surfaces and edges pretty flat and true. I think this might
be why there seem to be more 5 size planes around than any other -
this was the plane most craftsmen would have if they only had one
plane.

And a rabbet or sholder plane - the one I use the most is an old
Record 311, but the Stanley 92 or 93 work fine - if you do machine
work and then do the final fitting by hand then you will find yourself
using a rabbet plane a lot.

And because it is so small you might be able to sneak in a Stanley 101
- this is a little 3 1/2" very simple plane - looks almost like
something out of a kids tool set (I think they might have been) - but
pretty inexpensive (about $10 if you hunt around), and very handy for
a lot of small jobs like easing edges. I think I always have one of
these in my apron pocket - and have given a lot away to friends who
have gotten pretty attached to them.

The book on hand planes by Garret Hack has a lot of good information
in it - just be warned that once you start making nice paper thin
shavings you won't want to quit - is great therapy. Have fun whatever
you do.

Stephen