Learning about different problem solving strategies and when to use them will give you a good start. Problem solving is a process. Most strategies provide steps that help you identify the problem and choose the best solution. There are two basic types of strategies: algorithmic and heuristic.
It should be 'No vacancies' (plural). Vacant means empty/free. Vacancy is the state of being empty, therefore 'no vacancies' = no empty rooms.
No vacancy because of you There's no vacancy, no empty rooms Got no vacancy ever since I met you No vacancy because of you [Chorus] Used to be that I felt so damn empty Ever since I met you, no vacancy Used to be that I felt so damn empty Ever since I met you, no vacancy No vacancy, no vacancy [Bridge] Come on, come on, listen, oh yeah Come on, come on, listen, oh yeah When I fell, I fell, I fell, I fell for you So no vacancy, no vacancy [Chorus] Used to be that I felt so damn empty Ever since I met you, no vacancy Used to be that I felt so damn empty Ever since I met you, no vacancy No vacancy, no vacancy [Outro] Come on, come on, listen No vacancy, oh yeah Oh yeah, no vacancy