Its not always possible to take the lane. In these situations I find looking over your shoulder a few times is sometimes enough to tell the approaching driver you intend to pull out. I always look a few times before I stick my arm out and have had people let me pull across lanes without having to indicate. I try to give people a little wave to say thanks too, they're more likely to let the next cyclist go if you are nice about it.
Its not always possible to take the lane. In these situations I find looking over your shoulder a few times is sometimes enough to tell the approaching driver you intend to pull out. I always look a few times before I stick my arm out and have had people let me pull across lanes without having to indicate. I try to give people a little wave to say thanks too, they're more likely to let the next cyclist go if you are nice about it.