I recently heard about the 'Gay Fanfiction Problem', which for those of you who don't know, is a linguistic/writing issue that asks, "When discussing two characters of the same gender, how should pronouns be handled as to avoid confusion?" Say at some point in your story, Marcus spots Samuel at a party. You can't say "He saw him" without establishing who is who. There are many solutions to this problem. The easiest -but clunkiest- solution is to avoid pronouns altogether, instead saying, "Marcus saw Samuel." The issue then arises when you have to reiterate the character's names over and over, ad infinitum. In some languages, there are different pronouns for different social standings, subject/object differentiation, among other distinctions. English isn't one of those langauges, but if need be, you can simply refer to a character by a trait. Hair color, physical fitness, and personality all work fine. Obviously, in context, you'd probably only have to specify one name, with the other being the established subject, but when this problem does comes up, how do you solve it?
Ugh. Ran into this a ton when I wrote the second half of The Belly and the Boy. Try to alternate. if you identify one character by name in one sentence, switch to identifying the other by name the next. Try to cut down on the number of subject switches. With 2 different genders, you can do a lot of very quick back and forth, even in the same sentence. With 2 characters of the same gender, it can be better to have longer sentences or paragraphs that only mention 1 of them. This does lower the pace of action, though, which may or may not be what you want. Try avoiding labelling characters entirely. Your readers should have ways of telling 2 characters apart by what they say and how they say it. If one character is angry and the other is apologetic, you don't have to attribute every line they say to a character, it'll be obvious from the way they speak. I wouldn't try too hard for alternate identifiers, like "the taller guy" or "the linebacker". It gets gimmicky quickly (repeat that 10 times as fast as you can).
I’m guilty of really disliking characters being referred to alternately by their name, or their hair colour. “The brunette sighed”, really irks me but I’m also very much guilty of using that technique as well when I need to. I’m a hypocrite like that, annoyingly. Accents can come off a bit weird in written text but vocabulary is one way to make it clear who’s talking at least, without having to constantly clarify whether it’s Marcus or Samuel. If they’re having a conversation, you can also assume that they’re alternating like a duologue, and just have the dialogue there. i think one other useful way might be establishing mood? If Samuel is more emotional than Marcus is the scene, maybe the way he’s doing things is different, and the reader can be trusted to infer that Sam is the “he” who’s trembling etc
Similar to what TheLowKing said, I usually try to follow your rule - name both characters initially and only use pronouns for the last one who was the subject of a sentence. When the other one acts and becomes the subject, then the pronouns switch. Marcus saw Samuel at the party. [Marcus is the subject] He couldn't believe Samuel would show up. Not after what happened. His eyes narrowed and he crossed the crowded room, leaving his date standing there bewildered. "How dare you." He said. [All the "He"s are Marcus] Samuel winked at Marcus. [Samuel is now the subject] He looked up at Marcus with those big brown eyes. "I wouldn't miss it for the world." He grinned. [Now the "He"s are Samuel] It's not perfect but it works for me.
I tend to use a lot of names and descriptors, evaluate possible points of confusion during the sentence, etc. With any given individual character you usually have a choice of names to go by - the Invisible Woman, Sue Storm, the heroine, the blonde heroine (if there are any other blonde non-heroines or non-blonde heroines in the scene), etc. It's really no different than mixing it up so that you're not using the character's name all the time - so Superman can also be the Last Son of Krypton, the Man of Steel, the Man of Tomorrow, the Kryptonian, etc.
These are very good for making back-and-forth dialogues flow, but I think the tricky part is when both Marcus and Samuel are mentioned in a sentence together, particularly a complicated one with more than one clause. That's where we can start getting tripped up. Let's say we have: Marcus smiled. He reached out, his fingers caressing Samuel's cheek, before bringing his face closer for a kiss. In this case, "he" (the subject) is Marcus, the first "his" definitely also belongs to Marcus, but what about the second "his"? Whose face got brought closer? Depending on the context, each possibility subtly changes the dynamic between the characters, implying that Marcus is taking more or less control in the situation. As Elfie mentioned, the best scenario is that the reader already knows the characters well enough to correctly guess which way round it is, but there must be situations where it just gets messy. To take another example from a recent chapter of mine, which I had to look at a few times when I was writing it: Willow moves to look into Lux’s eyes, to cup her face in her hands. Here we have two uses of "her" in the same clause of the same sentence, yet referring to different people. Hopefully, it's clear from the context in the chapter that Willow is cupping Lux's face, but it's also possible to cup your own face in your hands. So I feel like it's at least slightly open to being misread that way.
I think my fallback in this scenario is to use names or other descriptive terms a lot. It might be clunky but at least it should be clear for the reader.
I’m about halfway through my story’s first proper FF pairing and I’ve been obsessively checking this thread for everyone’s advice! Thankfully one character is a Tiefling and the other is an Elf, so I have some extra descriptors there, but I think I’ll still probably have missed the mark here and there!
Marcus has three consecutive actions leading up to "bringing" and has his hand on Samuel's face. So as I read it he is clearly in control in the situation regardless of whose face moves. If the distinction has an impact in the story then I'd make it more explicit than that. IMO the issue is trying to compound too many actions into a single sentence. Extra verbs like "moves to" and "reached out" can almost always be cropped, and "looked" can commonly be replaced. Willow cupped Lux's face in her hands conveys the same to me, the eye contact being inferred by the physical contact.
True, it's just a good thing to pay attention to, as you say. That's probably fair - in intimate scenes, I guess I'd tend to try and pace these kinds of actions slowly so that they're gentle and deliberate, but maybe I'm overdoing it.