It can be something you read on a crisp packet, a conversation in the street you overhear. Sometimes you start with a character, sometimes a line of dialogue, sometimes a concept or a place or an event. They all start differently. There is no right way to start them off.
Writing a scene is really about throwing a series of questions at yourself.
Keep firing these type of questions at yourself until it feels like you were there.
If anyone asks you a question that you did not consider, you should still be able to answer it convincingly very quickly as you have made this scene so real to yourself that you know it backwards.
This is similar to the character psychoses and the location themes but covers recurring plot themes that are not character or place dependent.
These are metaphorical themes that run throughout your novel and add another artistic layer to your text.
At the beginning of the novel, when you are staring at the blank white pages in front of you, you need to trawl your imagination as you are building everything from scratch.
As you progress through various drafts of your novel, it will start to make natural links you hadn't even spotted. Don't try and make it too complex to begin with, but build it up in layers.
Writing fiction is really not much different from travel writing. In travel writing you go off to a place and spend X number of months/years there and take notes on what you see and who you meet and then distil all this into a book.
In fiction writing you do exactly the same. The only difference is that the places and people don't exist. You create an entire world in your head and spend X number of months there and then you write about it.
Always base scenes, people, events on real life. But not by a one-to-one relationship. If you base a wedding on a real wedding you have been to then you can only write as many wedding scenes as actual weddings you have attended.
Many people criticise long novels and use the classic phrase, "It took a while to get going and was a bit slow, but once it did, it was excellent."
Usually the reason it became excellent was due to all the build up.
If you introduce a character in chapter one and then kill them off in chapter three, many of the readers won't care too much.
One of the most mysterious things to try and pin down and study within the plot of any novel is the twist.
That moment in a book where a revelation hits us and, although it is a shocking surprise, we suddenly see that this point in time has been building throughout the plot. Suddenly we see that the build up that was leading us down one avenue was an optical illusion.