How to identify series or parallel combination in a complex circuit?

Series circuits are connected in a long chain from one terminal of the battery to the other. 
For Example: Some christmas lights you just bought at the store have an internal series circuit, so if you take out one little bulb or light, the entire circuit shuts off.
Parallel circuits form more than one continuous path for electrons to flow.
Ex: if you take out a little bulb from the lights only that part will shut off, not all of the lights.