There are very few rules but shooting when the sun is at its highest is usually a bad idea. Around the middle of the day it can be directly overhead which results in unpleasant shadows, especially with people. Up to three hours after sunrise and three hours before sunset will yield better pictures. The light then is coming from a lower angle so planning is necessary to make sure you are in the right spot to take what you have in mind.
In the past the best and first thing to do was to head for a souvenir shop and look at the postcards on sale there for ideas. That can still work but today you can use Google which can do pretty much the same thing.
Try and work out the time of day when the ones you like were taken; a church might look at its best in the morning with a lot of architectural detail visible but in late afternoon it could be just an outline silhouette.
Planning is essential at a large parade and knowing where to stand can make a huge difference between good and not-so-good shots. If you cannot visit the location prior, either study a good map and with the compass direction or look at it on Google Street View. You should be able to work out where the sun will be so you can plan where to stand. In a city a crossroads corner position gives several angles and also there will be a gap in the buildings to let the sun hit the subjects. An easy ‘rule’ to remember is to get the sun over your shoulder. But sometimes it is better to have it three-quarter backlit to produce better facial modelling.
With views and landscapes, try and frame a foreground object to give the picture greater depth which will lead the eye into it; a tree, archway, signpost or a road going into the distance are easy to find examples. If there is time, most places or subjects should be explored, that means you could put together a photo story.
Detail and close ups for instance can sometimes sum up an entire situation in a highly creative and conceptual way.
Whatever you do, have fun with your camera and always remember that it is just a device for telling a story, what that story can be is up to you!