Writers are fundamentally creators of new things and explorers of possibilities.
Time travel was invented by writers. Various authors have been credited with the ability, most notably H G Wells with his publication The Time Machine, but it could be argued that Charles Dickens' A Christmas Carol was the first being produced 50 years before. In fact an 18th century writer produced similarly speculative work which was subsequently destroyed.
Authors have created a myriad of books on dystopian societies and the factors that brought them about, yours truly also - Cessation which is available from all good book shops and associated websites. They create fantastic lands, terrifying adventures, romantic trysts and many other unusual and completely fictional scenarios.
When you sit with the keyboard and a blank screen before you one reason starting can be so difficult is that there are no limits, no regulations and only the boundaries of your own imagination to hold you back. That makes a pretty large choice you have to make. The most important step is to write the first word.
Like the proverbial elephant -
There is a decision to make that actually may occur quite frequently and that is how far away do I go from reality? In my Steele novels I have tried to keep close to reality and concentrated more on the plot but there is always the possibility of creating new weaponry. In fact he does have a gun that is undetectable by the metal detectors at airports which was based upon a suggestion that the CIA had produced such a gun. In fact there have been such weapons created for film.
An area that lends itself to being tinkered with is transport but when you consider futuristic films many alternatives have been tried before. The point is that it is up to you, the writer, to choose what artefact you are going to 'tinker with'.
You also invent people. They may be based upon someone the writer has known or bumped into or a complete fabrication. There is a pretty fair chance that something of the writer themselves will form part of someone's characteristics in their writing. Steele, my lead character is a mixture of James Bond and a likely rogue such as the Artful Dodger. There are some elements of me and quite a lot of purely fictitious stuff that are an amalgam of my ideas and feelings. If asked seriously how much of me there is in Steele I would have to say quite a number of facets but excluding the more violent side. In some ways it is a method of extending ones own existence and living alternate lives.