These notes present various priority arguments in classical computability theory, effective model theory, and complexity theory in a uniform style. Our notation usually follows Soare (1986) with some exceptions. We view Turing functionals as c.e. sets Φ of triples ⟨x, y, σ⟩, denoting that Φ(σ;x) ↓= y. (Of course, we have to impose the obvious compatibility condition, namely, that if ⟨x, y, σ⟩, ...