Fire Emblem: Three Houses - How To Recruit Characters From Other Houses
In Fire Emblem: Three Houses, you're not stuck with the roster that you start with. If there's a student from a rival house who catches your eye, you can try to woo them over to your side. Want Dorothea's healing powers, even if you're not a Black Eagle? Eyeing Raphael as your new tank? No problem. Go out and get them.
Aside from the house leaders and their seconds-in-command, almost every student — and most faculty members — can be recruited to your faction, which is a great way to both bolster your team and weaken your rival houses. You'll know which students are recruitable because you'll see a "Recruit" option on the menu after you speak with them in the monastery during your days off.
Choosing "Recruit" won't add those characters to your house right away, however. At the beginning of the game, most of the students are pretty happy where they are. It's worth trying to recruit them anyway, however, because even when they shoot you down, Fire Emblem: Three Houses will tell you which stats and skills you need to raise in order to get that kid's attention. The Blue Lions' Felix, for example, values Swords and Speed, so you'll need to get those reasonably high before he'll join you.
Support rankings help with recruitment as well. If a character has a high Support with Byleth, your main character, you won't need your stats or skills to be quite as high in order to recruit them. If you're trying to recruit a member of a rival house, invite them to meals, choir practice, and other social activities. The better that a student knows you, the more likely they are to jump ship and join your team.