Preparing a last will and testament - what do I need to know, and why should I create one?

I’m not yet 30, but it doesn’t hurt to ask.

When is a proper age, reason, or time to create a last will, and should it be legally bound? In other words, should I implement one through a lawyer?

I guess you’re wondering, what do I have that’s valuable. Well, not much (no cars, houses, businesses), but I do have other valuables or accounts that I would want bequeathed (properly), including online accounts (this is legitimate territory)?

Just want to know your thoughts, expertise….