This post will mostly apply to the USA. However, everybody will die at some point, and we can take care of some basic stuff before it happens to make life simpler to the ones that don't come with us to the other side..
Remember that I'm writing about personal experiences and own knowledge. I'm in no way intending to give financial or tax advice.
When we die, if no provisions had been made regarding their distribution, the state takes all our assets and distributes them based on state laws. A ' probation ' process is initiated, where a judge will end up deciding who gets what. This process will take time (it could take more than a year) , will have a cost (up to 5% of the estate, which is whatever we left in this world), and will lack of privacy (everybody will get access to the probate information).
Everybody, even somebody with few assets, can take some simple estate planning steps. Stuff that can be done once, and forgotten for years (but it is better to review once in a while, and it is mandatory to update it in case of divorce and perhaps such other bad situations):
Estate matters are very dependent on the law of each state, so my comments here may not apply exactly as I describe, but the basic stuff should be available everywhere.
Bank accounts and Credit Union accounts: Not every bank, but lots of them, allow registering a beneficiary in case the account owner dies. This is done by simply filling a form called TOD (Transfer on Death) or POD (Pay on Death), where can can write a list of primary beneficiaries and sometimes also contingency beneficiaries. The primary beneficiaries will receive the assets in case we die (many times we can specify what % of asset will each one get). The contingent beneficiaries will get the assets if the primary dies. TOD/POD are rather easy to fill forms, either paper or online, depending the institution. IMO, there is almost no excuse for filling up such forms. TOD/POD will baypass a will, and the bank will give the assets to the beneficiaries directly, without any probate! (The Willl goes to a probate, it can be legally contested). The TOD/POD, are final, afaik. Also, they don't have any costs.
Financial institutions (brokerage accounts, IRAs, 401k, etc): We can also fill a beneficiary form for these accounts, making it clears who receives how much.
Depending the state, for IRA and 401k, somebody that is married will need to put the signature of the spouse in case a non-spouse is put as 100% beneficiary. Although such assets would be given to the other spouse, I think that it is better to leave it in written (but if it doesn't matter at all, let me know :)
Will: Depending on the size of the estate, wills can be self-made or an attorney is needed. I'd suggest an attorney, they don't charge much for such a work (unless it is quite complex), and it is better to do this stuff in the right way. The will will go to a probate process. I'd prefer using POD/TOD/Beneficiary forms/Trusts to avoid a probate.
Trusts: The trust are the mechanism to avoid probate, but they are a more complex topic , not for this post.
Real Estate: If property is held individually, then the following article gives pointers to the Transfer On Death document in California ([https://www.sfchronicle.com/business/networth/article/Californians-have-a-new-way-to-keep-homes-out-of-6620601.php )
A general introduction to the topic in this article: https://www.fidelity.com/viewpoints/personal-finance/do-you-need-an-estate-plan
