Hmm. I don't want to hand my opposition a free guidebook of exactly what to avoid so they can do a better job of being a fed however, in general terms:

Feds basically try to "groom" people by convincing them of things - you deserved that position on the central committee, you should be the leader of your own party, you can trust me and we can plan out an adventure time, you are right to feel vengeful towards other party members. That sort of thing.

They seek to isolate people, generally the more psychologically vulnerable people (e.g. the ones who are too trusting or who are easily led by someone who sounds convincing and authoritative). A lot of what they do cannot be done in broad daylight, they need to be away from prying eyes to avoid being called out.

They encourage poor behaviour. They discourage people from reading, they discourage accountability and integrity, they discourage unity, they discourage good OpSec ("It's okay, it's just you and me - you can trust me. Now that I've gotten you all riled up about Donald Trump's reelection, tell me what you'd really do to stop him if you had access to the right resources.")

Always beware the adventurist. Not all adventurists are feds, and every radical experiences wistful thoughts about adventurism from time to time but the genuine adventurists are either prime targets for feds or they themselves are feds. Either way, hard pass.

They demonstrate a lack of fluency in theory and in the correct use of terminology. You know how a liberal fundamentally fails to grasp the Marxist concept of class? Yeah, that's what a fed is like, They'll try and they'll fail but they'll attempt to cover their tracks by gaslighting you and making excuses and doing shit like pretending to get stuck with the word on the tip of their tongue while they hem and haw and click so you'll feel compelled to finish their sentence for them.

They tend to be a liberal caricature of radicalism, of whichever flavour you happen to prefer. "How do you do, fellow leftists? You know I was thinking the other day about how Stalin did nothing wrong, amirite?"

They encourage hastiness (what a clunky word!) If you are slow and deliberate, you can be observant and you can notice when things aren't quite adding up. If everything feels pressured and you are being pushed to make rash decisions, then it is easier to steer you towards making a bad decision that can be very harmful in a variety of ways. Patience and being measured is anathema to feds and to wreckers.

They don't tend to offer up recent insights voluntarily from their studies. "Did you know that there were basically competing police forces in the Spanish Republic and they battled it out on the streets for primacy? Kinda wild to think, especially when the fascists were breathing down their neck at the time..." because they aren't learning theory and history on the same level as we are/should be, and also their understandings and conclusions often betray a liberal bias. So they generally avoid doing this, whereas comrades will be excited to share interesting things they have learned from their studies.

They don't like being pressed for more info. They tend to have a superficial understanding of things. They'll have their front constructed but as soon as you start probing their knowledge, they will desperately try to distract or avoid or do anything to salvage their cover. The best thing a comrade can do around a suspected fed or infiltrator of any kind is to conceal the depth of their own knowledge and pretend to be much more naive of theory and history than they are. This gives a likelihood of disarming the infiltrator and they will feel more complacent about talking themselves to the point that they have overextended themselves. The ones who flaunt their knowledge and who are very forthright with their positions and understandings are the ones an infiltrator will be very guarded around. There's roles for both types of comrades in an organisation but if you start getting suspicious about somebody then you have little to lose by hiding your power and biding your time while carefully observing to see if everything fits together more or less as expected or if things are incongruent. Apologies for being vague in what I'm saying here but I hope you get what I'm driving at without me being more explicit.

They can be cult-y. Trying to make splinter factions, trying to create a "family" out of a select group of people within the org, using drugs as a means for in-group bonding and loosening lips and for social control, fostering addiction with members who are prone to it. That sort of thing.

Comrades want the best for you and to see the best in you. They will guide you to be your better self, they will caution you against making errors, and they will try to build you up and encourage you to do the right things. Infiltrators will do the opposite. They will encourage the worst behaviours, they will guide you towards misconduct and malfeasance, they will try to break down your protections and find any gap in your armour to exploit. If they can't find one, they will try to make one. A comrade is one who you can count on to be the angel on your shoulder, guiding you towards the right things, while an infiltrator will the be devil on your shoulder, guiding you towards the wrong things. Didn't want to get all religious-overtonesy with you but I'm relying on metaphor to stay a bit vague here so that's what I've got.

Feds often start off good and then gradually dial up their shenanigans over time. You are the frog in the pot of water. Remember to check the temperature from time to time and don't rely on the fact that it was nice and cool when you first hopped in because all things change over time and that especially applies to feds.

Beware of the person who wants to get too close to you too quickly, who is too familiar too readily, and who tries to get more information out of you than they should.

We are probably all guilty of at least some of this stuff some of the time but look especially for patterns and trends. Everyone slips up sometimes but a moment of indiscretion or acting rashly is very different to a gradual trend in escalation of these things or a pattern of repeating certain behaviours or strategies over and over again.

Those are some of my thoughts.