O-Level Set language and notation

What the O-Level syllabus expects for Set language and notation, and how to practise it.

What the syllabus expects

using set language and the associated notation, including A ∪ B, A ∩ B, n(A), the element and non-element symbols, complement A′, the empty set, universal set, and the subset symbols A ⊆ B and A ⊈ B
the union and intersection of a pair of sets
Venn diagrams