proper wiring of a relay,
There are two schools of thought on this...

Option 1: Line to common..







simulate this circuit &ndash; Schematic created using CircuitLab

This is the classic way to connect it, and gives you the option to pick off the normally closed connection later if you need to.

Option 2: Line to normally open..







simulate this circuit

This method stops you from later connecting in the normally closed line, however it also means you do not have unconnected live terminals in the relay which may provide a safety benefit.



For most relays, electrically, and mechanically, it does not make much any difference. If your relay has special features, it may list a preferred connection method in the specification data sheet.

Failing any manufacturer instructions, which method you chose is really arbitrary. 



ADD: If you are using multiple relays within the same system, or even multiple products, it is however prudent to follow the same wiring on them all. Set a company standard as it were.

Do not have some connected live on common and others live on normally open. 

If your do you will just confuse, and potentially harm, whomever is working on it, and probably even yourself.