i cross over the line if it's a wide road, and i can see if there's any cars approacing from the opposite direction. i VERY rarely filter up the inside, only if i were to turn left and if the turning in mention is close. drivers wouldn't expect to see a motorbike on their left. imagine if they had to move over to the left due to a parked car on the other side of the road and oncoming traffic swerving around it. they'd crush you, on the right you have room to get around, on the left, you'd just go straight into the gutter. i try and sit evenly with the front car at lights, but accelerate to get in front of them when they go green (not cutting anyone up ofcourse) just need to look for junctions, cars turning right, cars entering your lane and swinging out (vans etc), looking for parked cars up ahead to see if cars will move out to avoid it. pedestrians walking in between cars and stuff