Keep your hand on your wallet/purse especially when walking around the old town & las ramblas. I had mine temporarily stolen by a woman begging for money and food. She shoved cardboard into myy side and whilst I was distracted stole my wallet. I managed to get it back (thanks for the concern).
Port vell and the nite clubs (discoteca) there... I guess it's ok that you can wander in and out of 5(?) nite clubs next to each other... But not these ones! One is just tackier than the other. Avoid. (If you like tacky places, then go for Port vell:)
All those tourist-oriented bars 'alongside' main streets ... just check if you can see some spanish people seated: if not, leave the bar ...
There's an exception to this rule: tapas bar are usually crowded of spanish people even on touristic paths ... so trust them !!
Benasque - doubtless good for access etc but unless you go for this do not bother.
(Photo unconnected - Hecho)