Well, there isn't any particular way, I just started looking at traditional startups on angel list that were making/doing things related to crypto, then quickly became interested in decentralized uncollateralized algorithmic stablecoins and started contributing with pull requests and community discussions. From there I just followed my own interests.
> What are the trends, top dApps and sites, Discord servers?
You'd cant go wrong familiarizing yourself with things like decentralized exchanges, decentralized lending (that run the gambit from over collateralized to uncollateralized) protocols, stable coins of various designs (decentralized or not) and concepts like staking, yield farming, liquidity pools, oracles, flash loans. With those terms, should be enough for you to DYOR and see if anything interests you to dig deeper (its ok if non of it does).
> How do you follow the meta?
I don't. I narrow in on the topics that most interest me from my experience working in tradfi and look for analogues in defi, I look for ways defi can make the barriers to do such things accessible to people that don't work on bank desks.
>It’s hard to find the signal when crypto and DeFi by proxy are already so spammy and noisy.
Yeah, i can understand that may be the case when one is mostly looking for "top" stuff and not topics/communities that may genuinely interest them (i.e. have a particular finance topic in mind) that people are trying to do in a decentralized way.