The techniques of sketching are the same whatever your subject. If you pay attention to proportion, relative positions of landmarks, angles, basic shapes and volumes, contours, negative space, local value and color vs. light and shade, contrast, construction, texture- all the usual stuff- you'll learn a lot. I suggest you start with small, quick sketches - concentrate on the basics - rather than jumping right into fully rendered sketches. Buildings and landscapes have so much detail it's easy to get bogged down drawing every brick or blade of grass if you don't force yourself to stay broad.
A ruler or t-square, about as long as your paper or a bit longer, is handy both for drawing straight lines and for checking angles and proportions.