I love Montreal, but like every destination, there are things you should and shouldn't do when you visit. (On) (a twist on) (the ever popular blog meme), here is my list of things to avoid doing at all costs when visiting Montreal.
A meme is
an idea, behavior, or style that spreads from person to person within a culture
The writer is pointing out how everybody makes a cliched blog post along the lines of:
Top ten things to do in (some city)
Best places to eat in (some city)
Most beautiful sights in (some city)
and calling this a blog meme.
The phrase "A twist on" means a variation on. So if a friend introduces me to a new sport named "Gobbledygook", which is a modified version of Soccer, and I ask
What is Gobbledygook?
He would respond
It's a twist on Soccer.
So the writer is saying their list of things to not do in Montreal is a variation on the overused style of travel-related lists in blogging.
Also, the phrase should be
In a twist on
not on a twist on.