Even when birding with a scope at hand, it's best to start scanning with binoculars first, before using the scope. You'll cover more territory looking through your bins, and will be able to locate birds more quickly. To get the desired view, first set the scope on wide angle - zoomed out - and pan to find the bird. Then zoom-in slowly to bring the bird closer, adjusting the focus while you do so. Keep in mind that a zoomed-in view is not always the best one, as this magnifies heat waves and motion, which could make the image blurrier. You may prefer a farther-away but sharper view.
photo © adrian binns