There is lots of anticipation and timing involve when you have to move from one lane to the next when those lane you are in becomes left turn or right turns only lane. I have one stretch where the right lane will become a freeway entrance lane and car from behind is already picking speed while still in the city road so that they can get on the freeway faster. Sometime even taking the lane can be an adventure in my case.

The key is about total awarness and trying to time yourself with what car is approaching well before getting to the intersection. I'm not talking about 100ft but rather at least 200+ft of planning. Try to remember cars you do spot in your mirror can be right next to you in a blink of an eye. During that blink, you can easily lose your oppurtunity and timing to take the lane or merge over. Time your speed way ahead so that you will be between pockets of cars when you approach the section where the lane become right turn only. Then go ahead and take the lane, recheck to see if cars on the left lane wants to enter into your lane, then safely enter into the main lane.