Reference:

Ladefoged, P., & Johnson, K. (2014). A course in phonetics. Cengage learning.

Rules for English Consonant Allophones—Ladefoged
1, Voiceless stops are aspirated when they are syllable initial
2, Voiced obstruents are devoiced at the end of an utterance or before a voiceless sound
3, Voiced stops and fricatives are voiceless when syllable initial or preceded by a voiceless sound
4, Voiceless stops are unaspirated after /s/
5, Voiceless obstruents are longer than the corresponding voiced ones when at the end of a syllable
6, approximants/w, r, j, l/ are partially voiceless when preceded by initial /p,t,k/
7, stops are unexploded when they occur before another stop
8, syllable final /p,t,k/ are often accompanied by an overlapping glottal stop gestureˌ tip/tɪʔp/
9, /t/ is replaced by a glottal stop when it occurs before an alveolar nasal in the same word. beaten /biʔn/
10, nasals are syllabic at the end of a word when immediately after an obsturent.
11, /l,r/ are syllabic at the end of a word when immediately after a consonant
12,/t,d,n/ become voiced alveolar tap when in the middle of two vowels
13, Alveolar consonants become dentals before dental consonants
14, Alveolar stops are reduced or omitted when between two consonants e.g. goo(d) night
15, A homorganic voiceless stop may occur aftera nasal before a voiceless fricative followed by an unstressed vowel in the same word. Insert epenthesis, e.g. stops /p,t,k/, in the middle of words between nasal and fricative （e.g. /sʌm p θɪŋ/, /jʌŋ k stɚ/, /pɹɪn t s/)
16, A consonant is shortened when it is before an identical consonant e.g. goo(d) day
17, Velar stops become more front before more front vowels.
18, /l/ is velarized when after a vowel or before a consonant at the end of a word.

Rules for English Vowel Allophones–Ladefoged

1) other thing being equal, a given vowel is longest in an open syllable, next longest in a syllable closed by a voiced consonant, and shortest in a syllable closed by a voiceless consonant.
2) Other things being equal, vowels are longer in stressed syllables.
3) other things being equal, vowels are longest in monosyllabic words, next longest in words with two syllables, and shortest in words with more than two syllables.
4) A reduced Vowel may be voiceless when after a voiceless stop (and before a voiceless stop).
5) Vowels are nasalized in syllables closed by a nasal cononant.
6) Vowels occur in syllables closed by /l/. add a vowel [ʊ] before velarized [lˠ]
e.ɡ. peel [pʰiʊlˠ] pail [pʰeʊlˠ](omit the second element of [eɪ] to show that the vowel moved from a mid-front to a mid-central quality) pal [pʰæʊlˠ]

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