To get the best weapons fast,
head to the extreme northwest
of the map. There you should
find a mutant gaurding the gate entrance. He has a laser
rifle, about the 4th most powerful weapon. He is isolated from his 2
partners, and should be fairly easy to kill with a few grenades, or
maybe even a pistol (if you save and reload alot)
This laser rifle should make battle elsewhere simple, and is even decent
against the other mutants (the lasers are very valuable).
if you go inside you will find some rocket launchers. You need to kill
the other outside gaurds and get the metal tape recorder. It has an
entry code on it. Inside red forcefields can be walked thru but yellow
ones require dynamite or c4 to disable. One of , if not THE best weapon
in the game , a gatling laser, can be found from a mutant on level 2 and
on level4.  But will probably be too dificult to get early on(even with
your need hi-tech weapons).This is a quick way to get excellent weapons
and money.
Another way to get great stuff is to first go to the brotherhood (south
of the vault) then to glow. Youll need a rope (you can get one in
downtown hub) to climb down the crater. Once inside search the dead
bodies. Youll find what they sent you along with a yellow key card. Use
that keycard on the sw elevator.
Then as you continue explorer you will find lots of neat weapons and
items, with no gaurds :)) AS soon as you find some rad-x take it, but
save all the rad-away til the end.
You will find a total of 3 key cards for three different elevator
shafts. Eventually on level 6 you will find a terminal with a generator
near it. Use your repair skill to fix it, then enable primary power. You
can now use the elevator to the nw. You can now access level 5, where
most of the good trasure is.
BUT there are many robots who now have power to defend it.
Use those EMP type grenades on them (try to wait til they all gather
together).
When you are done you will have alot of experience and too much treasure
to carry.
Carry all you can and head out . Use the geiger counter to see how much
radiation you have taken. The radx should of kept you below 500.. just
before you depart from glow use all the rad-away. You may be sick the
whole way home, but you will survive the radiation poisoning.

If time is running out and you are DYING to know where water chip is....
(warning this may SPOIL alot of the game) the chip is in the city that
starts with N.. in the northern most sewers (this particular entrance is
within a cell inside a building.)

Well that should be more than enough to get you started.