My main actual trick has been to be discerning in the things I sign up for and never filling in information that's not required.
Think you might want to save on paper and give out your email address when you register to vote? Dear god. San Francisco doesn't give voters the ability to only receive correspondence from the Department of Elections. The spam is insane. Obviously you get all sorts crackpots running for office that'll spam you endlessly. For a while I was even getting email about pet clothing from some guy. Turns out he ran a failed mayoral campaign and then turned around and used the voter rolls to promote his business (because clearly I want a tutu for my non-existent dog).
And, sure, you can remove your email address from the voter rolls but not your physical address (so that spam will continue unmitigated). San Francisco is an extra level of special here as it doesn't even bother with HTTPS for their Department of Elections stuff.
In...olden times when people ordered by talking to other people, you’d often pay cash. Some places would take credit cards, usually by reading the number out loud. One fancy place let you type the numbers in with the touch pad.
Card payments, contactless payments, Apple Pay, metro/travel cards and banks/financial institutions with fancy mobile apps have meant that I rarely if ever need cash.
I wouldn't go as far as to have no phone number whatsoever, but living without one doesn't seem entirely crazy to me.
Having a WiFi-only device (as opposed to a data-only one) did mean I had to plan things a bit, just like I had to do before mobile phones became such a popular thing. It wasn’t a big deal at all.
I guess I’m convinced that it could be done, but I’m less convinced that it makes sense, and baffled as to why you’d pay for a phone and then go to such lengths to avoid using it.
I answer the phone all the time and it's always someone I know. I do not have a caller id display.
Here's how I managed that.
Only 4 people know my real phone number and are under orders not to add it to any digital address book.
My phone number is registered to an alias. I pay for my phone using cash.
My area code is in a city I've never lived in and have no connection to.
I add my number to the do not call list.
For generic phone number requests, such as stores and shipper that demand it, it's always 555-1212.
Of course this method won't work well for people who need to give their phone number out to people they don't know. But then again if that result is simply not to answer the phone ever, why would that be better. And for those who really only ever want to hear from a half dozen or fewer trusted friends and family, this is a solution that works.