a is normally unmarked. In a syllable with no other sounds, it is written ཨ་ (a). Also, in some syllables that end in consonants, it may be necessary to write out "a" as ཨ (a), although this is never done in Tibetan; this is done to avoid ambiguity as to which consonants occur before and after the vowel. Note that this is never necessary with other vowels.
b བ (b)
c ཤ (sh)
d ད (d)
e ཨེ་ (e) - note that this, like other vowels, is a mark that appears above other letters
f ཕ༹ (f)
g ག (g)
i ཨི་ (i) - note that this, like other vowels, is a mark that appears above other letters
j ཞ (zh)
k ཁ (kh)
l ལ (l)
m མ (m)
n ན (n)
o ཨོ (o) - note that this, like other vowels, is a mark that appears above other letters
p ཕ (ph)
r ར (r)
s ས (s)
t ཐ (th)
u ཨུ (u) - note that this, like other vowels, is a mark that appears above other letters (or, in this case, below them)
v བ༹ (v)
x ཧ (h)
y ཨྀ (-i) - this is a special character which was added to the Tibetan script in order to transcribe words from Sanskrit (it's actually just an i backwards). It is actually intended to write vocalic letters, which would be a reasonable purpose in Lojban, except that I find it's use for "y" to be more compelling.
z ཟ་ (z)
ai ཨཻ (ai)
au ཨཽ (au)
Note that "ai" and "au" have special symbols which were added for the transcription of Tibetan. For other Lojbanic vowel diphthongs, it is necessary to use the Tibetan semivowels:
i in a diphthong becomes ཡ (y);
and u in a diphthong becomes ཝ (w)
in the case of uu, ui, ii, and iu, it should be the first vowel which takes on its diphthongised form.
' འ (') this character is used in Tibetan to write vowel diphthongs, as well as a sound which has since been lost from the language, but which was apparently somewhat like an h.. The second vowel is written above or below the achung; if none is written, that signifies an "a"
. ། (/) - this mark is used in Tibetan to show the end of a sentence (much the same purpose for which the period is used in most languages).
.i ༏ (;) - I like to use this mark as a shortcut to write ".i" It's original purpose was to mark the end of a paragraph or series of sentences.
, ་ (space bar) - this mark is generally used after every syllable in Tibetan, and so I suggest that it should also be used as such in Lojban (except that it be not used between syllables separated by a '). This leaves the question of how to arbitrarily split lojban consonant clusters into syllables. I propose that, in the case of gismu, the first syllable should always be written as if it ended after the first vowel; this will show the consonant clusters more clearly. In the case of lujvo, syllables should, naturally, break between rafsi (y should be written as a separate syllable). As in so many other aspects, no consistent rules can be formulated for cmevla, although if it particularly resembles a rafsi or a lujvo, it is best to use those rules (i.e. "la ci,zras." ལ་ ཤི་ཟྲས་ and "la gliban." ལ་ གླི་བན་); even so, there a few cases of words that resemble both lujvo and gismu, most notably "lojban", which resembles both the tanru of seltau "logji bangu" as well as the gismu "lojbo". I prefer to write it as a lujvo: ལོཞ་བན་
A ཨཱ (A or aa) - this mark is used in transcriptions of Sanskrit to show long vowels; we can use it represent syllable emphasis in cmevla; e.g. བཱ ཨཱེ ཅཱི དཱོ ཕཱུ༹ གཱྀ
vocalic r and n རྲ ནྣ (rr, nn) - this can be showed simply by stacking the letter on top of itself
some samples:
.i la lojban mo ༏ ལ་ །ལོཞ་བན། མོ་
la nicte cadzu ལ་ ནི་ཤྠེ་ ཤ་དྯུ་
xekri je blanu nicte ཧེ་ཁྲི་ ཞེ་ བླ་ནུ་ ནི་ཤྠེ་
e'osai ko sarji la lojban. ཨེའོ་སཻ་ ཁོ་ ས་རྮི་ ལ་ ལོཞ་བན་
la cribe pu finti le lisri ལ་ ཤྲོ་བེ་ ཕུ་ ཕི༹་ནྠི་ ལེ་ ལི་སྲི་
mi jinvi le du'u loi jmive cu zvati gi'onai na zvati vau la .iupiter. མི་ ཞི་ཞབི༹་ ལེ་ དུའུ ལོཡ་ ཞྨི་བེ༹་ ཟབ༹ཨ་ཐི ན་ གིའོ་ནཻ་ ན་ ཟབཨ༹་ཐི་ བཽ༹་ ལ་།ཡུ་ཕྷི་ཐེར།
mi catlu lo mlatu poi ke'a zbasu lei slasi མི་ ཤ་ཐླུ་ ལོ་ མླ་ཐུ་ ཕོཡ་ ཁེའ་ ཟྦ་སུ་ ལེཡ་ སླ་སི་