These are the symbols I intend to use in my phoneme tables.  More symbols will be added if, and as, necessary.
A note regarding rhotics:  I use [r] to represent a rhotic in languages that have only one such sound; the table row is for languages such as Hindi, which distinguish multiple rhotics.  In the former case, I also generally classify the rhotic as a liquid phoneme.

Consonants:
Note: x/y means "y is a voiced x".
 

	Bilabial	Interdental	Dental /  Alveolar	Palatal	Retroflex	Velar	Uvular	Pharyngeal	Glottal
Stop	p/b		t/d	[ty]/[dy]	t/d	k/g	q/G		'
Affricate	[pf]/[bv]		[ts]/[dz]	c/j	c/j	[kx]/[gx]
Fricative	f/v*	T/D	s/z	S/Z [c,]/[j,]	s/z	x/[Y]	q/G	h/g	h/h
Nasal	m		n	ñ	n	N	N
Liquid	w	v	l	[ll]	l	L	L
Rhotic			r  [r~]	r	r		R
Glide	w  [4]			y

*There are no languages known to distinguish between a bilabial fricative and a labiodental fricative, so these symbols are used to represent both.
[v] represents a labiodental liquid.
[r~] represents a dental trill.
[4] represents a labio-palatal liquid, found in French 'lui' [l4i].

Vowels:
Each pair of vowels is listed here as (unrounded),(rounded).
In cases of distinctions based on tense vs. lax, capital letters are used to represent the lax forms.
Tildes following a vowel indicate nasalization, eg [o~] for the vowel in French "bon" [bo~].
Extra rows are added in cases where height distinctions are of >3 tiers.
 

i, ü	i, u	u, u
e, ö	*, ^	o, o
æ	a	a

/*/ represents the schwa.
/^/ represents the "upside-down V" sound.

Special characters:
There are also some special characters used to modify the above sounds:
 

>	indicates velarization or backing of the preceding phoneme symbol.
'	indicates glottalization of the preceding phoneme symbol (ejective).
:	indicates lengthening of the preceding phoneme symbol (used in languages where length contrasts are not systemic).
h	indicates aspiration or breathy voice.
,	is a symbol used for various purposes, usually to distinguish apical from laminal phonemes. Also used in the digraphs that distinguish palatal fricatives from their alveo-palatal cousins.
.	is used for voiceless vowels & nasals.
n	(appropriately assimilated nasal) indicates either pre-nasalization of or the nasal release of a phoneme, depending on whether the nasal precedes or follows the base phoneme.

Other symbols are used for language-specific or family-specific features.