In this short video an officer from the Metropolitan Police shows how to lock your bike correctly, the same principals apply in Dublin as in London:
Often bicycles are stolen with little effort when it was locked poorly or a low quality lock was used. Here’s some tips to avoid being a victim to bicycle theft, based partly on advice given by the Gardai:
It’s recommended to spend at least 10% of the value of you bike on a lock
It’s also recommended that you use two good locks of different types and lock both to the frame and the wheels of your bike
Think about where you lock your bike:
Lock your bike to an immovable object, such as a bicycle stand, metal railing, lamppost or signpost
If it is not a designated bike stand be aware of blocking the path of pedestrians, wheelchair and pram users — out of respect for them firstly, but it is also more likely to get damaged if it gets in people’s way.
Be aware, if using a lamppost, sign post or bollard of the possibility of lifting the locked bicycle over the post or bollard and also be careful of loose poll.
Do not leave / park your bike in isolated, dark or dimly lit places.
When locking the bike:
Lock the frame and both wheels.
Be careful to not just lock your wheel to a bike rack or poll — a thief will easily be able to take your bike off your wheel and walk away with the bike.
Make sure to lock your bike securely — even if it’s not worth stealing it can be knocked to the ground and vandalised
Also remember to:
Take all accessories and easily removable objects with you.
Consider replacing quick release levers with normal nuts and bolts or with special locking nuts and bolts.
Try not to leave / lock your bike in the same place every day.
In New York, the now infamous Hal rates peoples locking methods, showing the best and the poorest locked bikes and everything in between (although stealing saddles isn’t as large of an issue in Dublin):