When you visit a special location to make a sketch for a painting or a larger drawing back in the studio, you need to capture as much information as you can.
Take lots of photos - think of details, view points and the play of light and shade.
Think about the main subject of the image and which parts you will work up and develop.
It doesn’t much matter if your drawing or sketch is problematic or ‘not very good’ since you need to understand that every problem and difficulty you understand is also a step on the road to making something better.
Reference and research a location - 7.45 minutes/ seconds
https://vimeo.com/album/3562125/video/140587657