Language awareness and systems: phonology, lexis, grammar and discourse
Phonology
You need the phoneme inventory, place and manner of articulation, and voicing (the feature separating /p/ from /b/). Keep phonemes and graphemes apart: English spelling is an unreliable guide to sound, so never treat letters as sounds. Suprasegmentally, know word stress (and its role in word class: REcord vs reCORD), sentence stress, weak forms of function words, intonation, and connected-speech features such as elision, assimilation and linking. English is stress-timed; syllable-timed descriptions belong to other languages.
Lexis
Understand word formation (affixation, compounding, conversion), collocation, chunking, register, connotation versus denotation, and the difference between a lexical set and a semantic field. Words are learned better as chunks than as isolated items.
Grammar
Analyse any structure on three dimensions: form, meaning and use. Tense is not time, and tense is not aspect. Know word classes, phrase and clause types, coordination, subordination and modality.
Discourse
Cohesion is the surface glue (reference, substitution, ellipsis, conjunction, lexical repetition); coherence is the underlying sense that makes a text hang together. A text can be cohesive yet incoherent.
Traps and a worked example
Questions blur cohesion/coherence, tense/time, and phoneme/letter. To check a learner's /ɪ/–/iː/ contrast, use a minimal pair such as ship/sheep (differing in one phoneme only), then check it in connected speech, where weak forms may mask the problem.