Unless you are an oracle and you know with 100% certainty that you will survive to the technological singularity some time during the 2040s, it is highly advisable that you write a will.
Of course, the legalities of a will vary from country to country, but usually a comprehensive and well-written will follows a pretty intuitive checklist.
Ideally, your executor (not to be confused with an executioner, which you probably wouldn’t want in charge of your fortune) should be young enough that in all likelihood they will outlive you, but not so young that they aren’t mature enough to handle such a delicate and important matter.
The executor is the person who carries responsible for carrying out the terms of your will. Furthermore, it’s preferable that your executor personally not have a lot at stake, since conflicts of interest may turn what is supposed to be a fairly straightforward and painless process into a family-destroying feud.
Also, it is advisable to not be overly conditional in your will. For instance, don’t be that jerk who says Mary can only have $200,000 of my money if she divorces Greg and never remarries him.
Not only will a clause such as this sully your reputation beyond the grave, but your conditions are likely to cause drama and legal hassles. Is that really the kind of legacy you want to leave for your friends and family?