By now, most English Language students would be studying informal language. Part of this topic is the ability to use metalanguage to correctly identify informal language features in both spoken or written discourse. To help you with this process, I have listed some informal language features below.
Main Features of Informal Texts (Spoken and Written):
Slang terms
Colloquialisms
Phrasal verbs (verb + preposition)
Contractions
Abbreviations/Acronyms/Initialisms
Ellipsis
Swearing/colourful language
Discourse particles (like, you know)
Interrogative tags
Diminutives
Simple and compound sentence structure – lack of complex/compound-complex sentences
Inference
Interrogative sentence types
Non-standard orthography
Capitalisation/Bolding/Italics
Exclamation marks
Features of spoken discourse
The use of deictic expressions
The use of personal pronouns (e.g. ‘I’, ‘We’)
The use of active sentence structure as opposed to passive
Beginning a sentence with a conjunction
Emoticons
Neologisms
Idioms
Assimilation
Elision
Reduction
Shortenings
This list is by no means complete! I am sure we could all still add more to it... feel free to comment below with other informal linguistic features OR if you'd like to know the definition of one.
I hope this helps!