Angel investment is a product and some people with products have marketing challenges.

A brief thread: https://twitter.com/kwuchu/status/1321482978132959232
All of the following presupposes that you actually have a product in the market, meaning (for angel investment) that you're accredited, that you have sufficient financial wherewithal to make investments, and that you understand mechanics.

If not, hit the Googles before founders.
Table stakes: update your professional spaces (Twitter, LinkedIn, etc) to mention that you're an angel investor, ideally with a crisp and focused pitch on wha you invest in and some indicia that you actually write checks.
Founders are playing a funnel game and trying to minimize for the number of emails (weakly) and conversations (strongly) they spend which end up going nowhere. If e.g. you are bandwidth constrained at the moment, be clear about that fact. (n.b. I am bandwidth constrained.)
(Bandwidth constrained is a polite term of art for "No amount of desire from my part to do this deal will actually get this deal done at this time", which covers a range of circumstances from "My wife has said no more this year" to "Liquidity can't cover check in next 6 months.")
Talk to people who are likely to be founders putting together a round in next few months more than you do currently. Peers talk. During these talks, which do not need to be about investing specifically, mention that you invest in <sketch out your themes/archetypes/etc>.
Talk to other investors who are in similar spaces/etc and who you think have good taste. Investors are at some level competitors, particularly for the best companies (because consumption of the product sold is finite), but at some margins cooperation makes everyone better off.
Brand your money.

"I can write $25k checks" puts you in a class with a few hundred thousand other people. "I can write $25k checks and I understand Japanese market entry better than anyone you know" pretty useful if a founder has that need specifically.
I will observe that you could position yourself better vis Japanese market entry than 99.999% of all professionals in the world with ONE ESSAY and if you cannot justify writing one essay (or podcast, or even a ten minute Youtube video) on the topic then maaaybe not in a business.
There exist an almost infinite number of hypothetical founder needs which would substitute for Japanese market entry.

You can similarly specialize in founder archetypes. "Design-first product people", "Engineers who can learn the business side", particular demographics, etc.
When you make an investment, attempt to turn that into marketing for your investing business.

Some people overindex on "z'omg how lame people are talking their book." You hope companies you invest in will eventually have a Marketing department, right?
Look to your left. Look to your right. Do you see a Marketing department for your angel investment?

No?

Then you are the Marketing department.
Be absurdly helpful to entrepreneurs.

Most angels do not add a huge amount of value. Many leave it to founders to tap them for their expertise, which results in about 0 emails.

Respond to investor updates. Reach out proactively. Refer candidates. etc, etc
You want your founders to tell their friends/etc "You are starting a company? Get $NAME on your cap table. The most useful person I could think of in [your space/their specialty, which will be key to your business/etc]."
Make the product experience good.

Be extremely respectful of founder time. Sounds obvious, but isn't for some people: clearly communicate timelines, show up to meetings on time, close quickly and wire quickly or give a firm no quickly.
I tell people (when I am investing, which see above am not doing actively at the moment) "I understand the SaaS business very well. One conversation for one hour. Send me your deck or memo beforehand. I will have a decision for you on a $Xk check within one hour of meeting."
Oh I forgot about this:

While the best way to start writing checks in next 3 months is to talk to people who will raise in next 3 months starting today, the best way to write checks in 5 years is to talk to people who will raise in 5 years starting today.
I expect, over the lifetime of my angel career, to make most returns from investments of the general shape "Based on our work together or rubbing elbows online, I think it is virtually inevitable you will found a company some day. When that happens, please call me. I will invest"
Founders do not soon forget the first person to ever treat them like an entrepreneur and/or peer.
"How would you know someone would inevitably found a company 5 to 10 years out?"

If someone strikes you as the 99th percentile in intelligence and drive of everyone you know professionally then that is an extremely likely to pay off bet and it costs you nothing to make the offer
(I will observe that on leaving employment at intelligence-/drive- dense places, people will generally mail their personal professional contact information to many close colleagues, and they will get same from soon-to-be-ex-coworkers.)
(Make sure you do that unless you have a very, very accurate crystal ball as to what will or will not be interesting conversations for you to have in 5-10 years.)
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