Simply put for every romance:

• When he/she calls you always accept his/her requests right away
  
• Be supportive and friendly with his/her
  
• Don’t accept money from him/her when he/she offers it
  
• Pick all the “physical” dialogues to get closer to him/her (like kissing him/her)

Romances are not exclusive. It's possible to do multiple romances in one run, but obviously you won't be able to do all because of the gender requirements.

From some of your comments it sounds like you don't need to be 100% supportive all the time, but the tendency needs to be there.

About the gender requirements: It looks like you need only the majority of female/male parts. So there is voice/genitals/body. I guess you need at least 2 of these to count as a female/male. Prove me wrong, we actually need way ore testing.

Beware of Spoilers ahead!

• Choose female character (female voice + female body (yes you can have a d, but also need boobs))!
  
• Complete all main missions until "Double Life".
  
• Do her side missions "Both Sides, Now " and "Talkin' 'Bout a Revolution"
  
• Side mission "Pisces": Don't abandon the plan!
  
• When you reach the penthouse where the gang bosses are sitting, pick the following dialogues:
  
  • “Let’s do this”
    
  • “Who are the other two?”
    
  • “Do my best. Jack ’em out”
    
  • “Hold on, think you’ve gone too far”
    
  • “[Draw Weapon] Let’s cut to the quick”
    
  • kill the gang bosses
    
  • “What?”
    
  • “You tried to cheat us all”
    
  • Doesn't matter if you kill Maiko or not. Both options work
• Side mission "Pyramid Song": Agree to the invitation and then spend the night in a hut.
  
• Pick dialogue “[Stand] Why not.”
  
• Kiss Judy in the bathroom.
  
• The next morning, talk to her at the docks and tell her that this was the beginning of something.

• During the first main quest, be sure to go to meet Meredith.
  
• Do not attack her or the guards.
  
• Don't choose the faction response unless you are Corpo.
  
• It doesn't matter if you take the money from her or not.
  
• It doesn't matter what you do with the money chip.
  
• Even if there is no chip, there will be a battle anyway.
  
• Kill all Maelstrom and get the spider robot.
  
• After some time, she will write a message to which you must reply that you start to like her.
  
• Then Meredith will offer to sleep in a motel.

• In second side quest:
  
• Invite her on a date at the movies.
  
• Select dialogue with a kiss to set off a romantic scene.

• Complete side detective missions.
  
• Rescue Randy during The Hunt.
  
• At the end of the quest, select the flirt option.
  
• In the next task, you need to kiss him on two occasions.
  
• The next morning, say that you enjoy being with him.

• Choose male character (male voice + male body parts)!
  
• Additional preperation: In the first story mission, you need to help her with Nash.
  
  
• On the mission, after saving Mitch, you need to ask the Panamas for help with Hellman and agree to deal with Kang Tao.
  
• When you find Hellman, you must select the option that it was not Panam's fault.
  
  
• First side mission "Riders Of The Storm": Ride with her.
  
• After saving Sol, choose the option: "Silly idea, Panam is right."
  
• The next day, when she goes to the motorcycle, last night must be mentioned.
  
  
• Second side mission "With A Little Help From My Friends": it is necessary to hide the plan of Panam from Sol.
  
• Next, agree to the assignment.
  
• On the control tower, you have to say that you missed her.
  
• After a few options, touch Panam's hand, telling her to follow the impulses.
  
• After a couple more options, you need to sit closer to her and say that it is getting cold.
  
  
• Third side mission "Queen Of The Highway": When you're done driving and shooting in the Basilisk, select the kiss icon.

• Choose male character (male voice + male body)!
  
• Complete side missions of Kerry.
  
• During the Off the Leash quest, flirt on the balcony.
  
• In the next mission, you need to kiss him.
  
• After the scene on the beach, you must select the option that initiates the romance.

• Literally part of main story.

I will add further information about for example exact mission names after my next run. But you can also just comment information and I'll add it with your name.
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