sa northbound hindi advisable na sa left lane ka palagi kasi bigla biglang nagmemerge right yung leftmost lane, at least 3 times (talk about dangerous and inefficient!) -- sa may ayala, sa may guadalupe, sa tapat ng megamall.
although, mas ok ang left lane... kasi may mga "emergency bay" na ginawa sa gitna ng MRT stations... yung is tapat ng nepa-q-mart... yung isa bago mag cubao...
I usually stay at the leftmost lane except:
(1) In the crossing and cubao underpasses where I try to dodge the "free carwash" from the leaky water pipes.
(2) When the leftmost lanes merge to the middle lane --> ex. Guadalupe Bridge going to Makati, Edsa Ortigas flyover approach. In such cases, I switch the middle lane well before the merge. (Then I start cursing the drivers who try to muscle their way in...mga hindi marunong mag-merge!)
Sa second or third lane ako usually. Kasi sa innermost lane eh usually parang pagong ang andar. Tapos minsan sa bus lane. Hehehe. Minsan lang naman. ;)