How can I be subtle in inviting non-Muslim colleagues and neighbours to Islam?

The best tool that you have and that we all have is our character and we know this from the Prophet sallallahu alayhi wa sallam. When the Quraysh used to physically abuse him, verbally abuse him, emotionally abuse him, yet when he said, 'If I were to tell you there's an army coming behind this hill, would you believe me?' They said, 'You never lie, of course we would believe you.' So the character of the Prophet sallallahu alayhi wa sallam trumped everything that they disliked about him, that they disliked about Islam. And so that's really the most important thing in terms of how we are as Muslims. We are all ambassadors for Islam, whether we like it or not, whether it's because of the way we look, whether it's because of the clothes we wear, whether it's because of the name that we have. We are all ambassadors in some way, shape or form. And your character, how you are as a human being, as a neighbour, being kind and being considerate, is really important in terms of the form of da'wah that you can give to those around you.