Writing a novel from a male POV isn’t only about thinking like a guy. It’s about talking like a guy.
One of the first things one might notice when comparing male and female speech, is that males use fewer qualifiers. For example:
Liz: “That test really, really sucked.”
Dan: “That test sucked.”
Similarly, you might notice that your female characters use more fillers when they’re searching for their words, whereas the male characters might be silent in that pause.
Liz: “Um, well…. I think I failed it.”
Dan: He paused. “I failed it.”
In A Cultural Approach to Interpersonal Communication: Essential Readings, Daniel Maltz and Ruth Borker point out that in male to female conversations, studies have shown that conversations take on a question and answer format, with the women asking the men more questions. They also noted that women tend to make more encouraging gestures and speech (i.e. “mm-hmm”) to keep the conversation going.
However, in your manuscript, I would advise against adding the ‘encouraging speech’ unless you are trying to show something specific. For example, if Liz was distracted:
“I took the sandwich,” Dan said.
“Mm-hmm,” Liz responded.
“Then I added all the hot sauce packets from the cafeteria’s condiment bucket.”
“Oh?” Liz continued filing her nails.
“I squeezed them all in Chris’s soup when he went to take a piss.”
Dan shook his head. “And then he took a big gulp and his face exploded. Liz, you’re not listening.”
(Note that Dan says, “You’re not listening” whereas Liz might say, “Dan, are you listening?”)
Interestingly, in the same article they note that men are more likely to interrupt the speech of their (female) partners, and are more likely to make statements of fact and to respond less enthusiastically about the comments of others (or to not respond at all.) They also note that men are more likely to introduce new topics or otherwise try to steer the conversation.
Deborah Cameron at The Guardian breaks it down another way and says that:
“Men’s goals in using language tend to be about getting things done, whereas women’s tend to be about making connections to other people. Men talk more about things and facts, whereas women talk more about people, relationships and feelings.
Men’s way of using language is competitive, reflecting their general interest in acquiring and maintaining status; women’s use of language is cooperative, reflecting their preference for equality and harmony.”
If you’ve heard from your readers that you male protagonist doesn’t sound like a boy/man, take a look at his dialogue and social interactions, and see if you can rewrite with these observations in mind.