If someone comes to me while I’m davening, I ignore them.
If someone comes to me by a simcha, I will usually give a dollar until I’m out of singles.
If someone knocks at my door, it depends on what they’re collecting for. I’ve told people that I don’t support the organization and won’t donate to it. I offer them a drink and a bite to eat, but tell them, sorry, nothing personal, I just don’t support this organization.