I hired one early this year through a "virtual assistant" company in the UK (Virtalent), as I don't need enough help for a full time person to be sensible, and they did a nice job of matchmaking. I had an initial call with one of their folks who spent some time going through with me what I'd want done, and then they set me up with someone pre-screened who I had an intro call with and liked. I'd previously tried FancyHands, and that required way too much micromanaging on my part.
paulcole's comment "Are you really ready to stop doing the things you're hiring this person to do?" is a bit on the nose. Learning to let go and delegate is key.
The biggest value I'd say I get is outsourcing decisions that aren't really important but are likely to cause my to spiral into "analysis paralysis". For example, hiring movers - if I tried to do it myself I'd end up spending hours fussing over reviews.
Another major thing is figuring out things I hate doing (phoning people, filling out expense reports, etc) and let my PA handle them.
It's also nice for me that she's British (I'm an American expat living in the UK) and is fairly experienced as an PA/EA and generally knows lots of things that I don't know I don't know. For example, when my partner and I wanted to have a special celebratory meal, she arranged a completely custom menu with a high-end restaurant, which didn't occur to me as something that I could ask for.
In this thread there are bunch of well-intentioned but vague answers that don't address the critical "how to find a good EA" part of your question, or answers that do address it via some kind of "virtual EA" service, of which there are many. This turns out to be a super common pattern; very few people really know how to systematically find good EA's.
Just a couple months ago I spent an absolute ton of time doing trial-and-error trying to hire a good EA, ended up wildly successful, and here's what I learned:
There are several methods for finding an EA, sorted below in order of goodness.
Method 0) Find an underemployed person working the front desk at some non-corporate institution, hire them for lucrative side jobs, escalate slowly. Good candidate institutions are poor NGO's, political parties, arts-and-culture related orgs like theaters, and language schools. Obviously this depends on you having access to such an institution, which is hit or miss.
Method 1) Freelancer.com. By far the best assortment of candidates, most enthusiastic replies, least-bad website. You can post a "Project" here searching for an EA with clear examples of likely duties and a brief description of compensation, and get a ton of inbound interest. Freelancer will eventually ban your account for this, because they can't figure out how to monetize this type of transaction, so use burner accounts and try to avoid posting Zoom links or phone numbers, which will trip their crude automated "customers cheating us" detector. Usually you'll get about 24 hours until banning, after your first attempt to contact a candidate off the Freelancer platform. Often they will preemptively assign you a "Freelancer.com employee to help you sift candidates, at no cost to you." This person is just a nanny who will scold you for being an unprofitable customer; they can be safely ignored.
Alternate approach: Hire EA candidates through Freelancer for a small one-off task, then transition to off-platform contact, this reduces bans.
Method 1.5) Fiverr, similar to Freelancer but varies by city/country more.
Method 3) Country-specific "Find a plumber/find a moving service" type sites. Examples are like maybe fixly.pl or Taskrabbit. Hard to generalize about these due to breadth, but mostly inferior results to the bigger international sites.
Method 3) Websites related to "hire a virtual assistant." Very spotty quality, hit or miss, many foreigners who don't actually speak your language. You really want a real person in your city, ideally in your neighborhood.
Whichever of these methods you use, you should follow a few very important rules (again sorted in order of importance descending):
Rule 1) Pay efficiency wages. Your EA is a you-amplifier; if she can perform some intervention in your life which saves a marginal hour of your time, you should value that intervention at close to the same price you assign to that marginal hour of your time (which is to say, astronomically, because you are a rich software person whose time is very expensive). This leads to things like "You paid $100 USD for your EA to semibriefly stand in line at the post office."
New EA's will be confused by the giant piles of money you are throwing at them, will wonder if it's a trick or a scam somehow etc. You will end up repeatedly emphasizing that you are not stupid, not throwing away money pointlessly, not dishonest, and in fact are acting rationally. Experienced EA's won't bat an eye and will take your money cheerfully.
Rule 2) Test EA's before making formal hiring commitments. Assign each candidate a (well-paid) trivial test task as an "interview." I use "here are 4 documents in a folder, with no envelopes and no stamps. Mail these 4 documents to 4 different addresses in various countries" as my test task. This is reducible to "find envelopes, find stamps, identify correct international postage, put right document in right envelope, stand in correct line at post office, do this in a reasonable amount of time" and it seems to filter the bad candidates. Obviously one of the documents should be sent to yourself, at your local office address, under some other person's name, so you can evaluate the tidiness/letter sealing/lack-of-coffee-stains etc.
Rule 3) Start by hiring your EA's on a freelance basis, e.g. pay a (task-dependent) bounty per task. Give them one task at a time, pay immediately after task completion via Venmo or whatever the equivalent instant electronic transfer system is in your country, then give them the next task immediately. At the beginning, don't have several open tasks at the same time.
Rule 3.5) At the beginning (and maybe permanently), let the EA control per-task pricing. E.g. instead of you saying "I will pay you $X USD to mail these letters," tell her "Please mail these letters, then let me know how much I owe you for this task, err on the side of charging me more rather than less." There are many good reasons for this structure, especially because you'll never know what delays/slow-moving-lines/problems occurred.
You may have to do a cute little reverse-negotiation wherein you negotiate the price up, often EA's will lowball the prices out of shame/fear/power asymmetry etc.
Have them make a Gsheet to track tasks, completions, and whether or not you paid. After several successful task completions, you can think about hiring them full time on a real contract etc. Very often you discover that you don't need a full time EA.
Rule 4) Avoid virtual EA's, you really want an actual human in your city and ideally in your neighborhood. Most people's lives and business contain a startling amount of boring/delegatable physical-proximity-dependent tasks; when you start looking for these and giving them to your EA, you will be shocked by how many there are.
Rule 5) When your EA quits because she got a better job (and she will, eventually, because anyone reliable/niche enough to be a good EA will eventually be hired by some rich business, often consulting or finance), ask her to hire her replacement by doing the procedure above, as her final task. Give a goodbye bonus as a token of goodwill. She will explain a bunch of context and unwritten procedures to the next candidates, that you weren't even aware of.
paulcole's comment "Are you really ready to stop doing the things you're hiring this person to do?" is a bit on the nose. Learning to let go and delegate is key.
The biggest value I'd say I get is outsourcing decisions that aren't really important but are likely to cause my to spiral into "analysis paralysis". For example, hiring movers - if I tried to do it myself I'd end up spending hours fussing over reviews.
Another major thing is figuring out things I hate doing (phoning people, filling out expense reports, etc) and let my PA handle them.
It's also nice for me that she's British (I'm an American expat living in the UK) and is fairly experienced as an PA/EA and generally knows lots of things that I don't know I don't know. For example, when my partner and I wanted to have a special celebratory meal, she arranged a completely custom menu with a high-end restaurant, which didn't occur to me as something that I could ask for.