Always take too many pictures. Never be prematurely convinced that you have THE shot. In the days of film unless you were a pro you has to be cautious – film/processing was expensive. A modest memory card of 4GB for example will allow you to store 300 images at least so go mad! Keep moving, keep you camera focused, compose your shot and most important of all release the shutter again and again and again. And again. Edit at home on laptop and not in camera as there is more danger of missing a crucial detail when pressing the delete button.
Please find below two shots taken over the past weekend. Not the greatest but the sunlight on The Shard and the girl with flame red hair in the second image help to elevate them from bog standard to not bad.. I took a lot of exposures approx 30 of each scene and the girl and the light only make an appearance in these two images.
Nikon D90 + AF Nikkor DX ED 18-55mm lens.