When you say "Do" what you're referring to is the Solfege, the singing technique for learning the 7-note diatonic scale as popularized in The Sound of Music.
Do = C
Re = D
Mi = E
Fa = F
Sol = G
La = A
Si = B (in the movie they used Ti, same diff)
Reference: http://en.wikipedia.org/wiki/Solf%C3%A8ge
The beauty of standard notation is that it's the same regardless of instrument. On the Treble Clef staff each line from bottom to top is E - G - B - D - F and every space is F - A - C - E.
The Treble Clef is also called the "G" Clef since the symbol encircles the G. Use this staff for Soprano and Alto voices.
You can remember them using the mnemonic device (E)very (G)ood (B)oy (D)oes (F)ine and of course, the other one is easily remember simply as FACE.
On the Bass Clef each line from bottom to top is G - B - D - F - A and every space is A - C - E - G.
The Bass Clef is also called the "F" Clef since the symbol encircles the F. Use this staff for Tenor and Bass voices.
You can remember them using the mnemonic device (G)rizzly (B)ears (D)on't (F)ly (A)irplanes [there's another one with more "good boys," but I find it confusing] and (A)ll (C)ows (E)at (G)rass.
While technically, the "Do" or C in the solfege can be written anywhere on the staves that there is a C, I believe that the song begins with Middle C which is one line below E on the Treble Clef (which is also one line above A on the Bass Cleff). Then, just like the alphabet, the musical scale increases in alphabetical order.
The more important question is what key your song is in. Because the key will determine how many sharps or flats it will contain. Sharps raise a pitch up one half step and a flat lowers a pitch one half step.
For example, the key of C major contains no sharps or flats. But the key of G major will contain one sharp: F sharp. You can use the Circle of Fifths as a reference, although I find that most people find it confusing. (Because let's face it, it is.)
Reference: http://en.wikipedia.org/wiki/Circle_of_fifths
I find it easier to remember the major and minor Interval Formula, but that can also be too much to learn for some.
For non-musical types, you can simply refer to a chart:
Reference: http://en.wikipedia.org/wiki/Key_signature#Scales_with_sharp_key_signatures
One of the simplest, easiest books on the subject is "How to Read Music: Fundamentals of Music Notation Made Easy" by Roger Evans. Inexpensive and straight forward.
Reference: http://astore.amazon.com/magnoliaguitars-20/detail/0517884380
Good luck and cheers!