Been there many times.. Here's what I found to be the best thing to do.
If you've already let them know how you feel about them and they responded with: I'm not looking for anything serious or I don't want to get involved at the moment. Then what you need to do is just give him/her some space and continue to be a friend. Hopefully they'll notice you're a good guy/girl and will come around. In situations like these you just have to sit back and wait for the person to be ready for a relationship.
Sometimes it'll work sometimes it won't but if you really like the person you would rather have friendship rather than no relationship right? Anyhow, good luck.. I know it sucks. Loving/liking someone that doesn't feel the same way about you hurts bad but you'll get through it. Hopefully the person you like will come around one day soon.
If you've already let them know how you feel about them and they responded with: I'm not looking for anything serious or I don't want to get involved at the moment. Then what you need to do is just give him/her some space and continue to be a friend. Hopefully they'll notice you're a good guy/girl and will come around. In situations like these you just have to sit back and wait for the person to be ready for a relationship.
Sometimes it'll work sometimes it won't but if you really like the person you would rather have friendship rather than no relationship right? Anyhow, good luck.. I know it sucks. Loving/liking someone that doesn't feel the same way about you hurts bad but you'll get through it. Hopefully the person you like will come around one day soon.