Open the aperture as wide as it will go. My 50mm, when at f/1.7, has such a narrow depth of field that I can see where the focus lies, utterly precisely, without zooming in. I mean, to the point where zooming in is of absolutely no practical benefit. So, instead of zooming in, I open up the iris, focus, then stop it back down.
After I got this lens, but before getting the K mount adapter I needed to actually use it, I tried practising manual focus using the kit zoom. It was hopeless; zoom was necessary. I wasn't looking forward to a manual focus lens at all. Once I used it, though, my opinion changed. It's all about depth of field; a fast lens makes focusing a breeze.