The best way to contact me is usually to email firstname.lastname@example.org. I try to be relatively responsive to anything that doesn’t look like spam. (Please don’t send me spam.) If you want to be especially private when emailing me, you can encrypt your mail using my GPG key.
Alternatively, my direct messages on twitter are usually open: @ajdecon. Responsiveness is probably similar to email — I mostly disable twitter notifications, so I only check DMs periodically.
I should also be reachable via Matrix at @ajdecon:matrix.svc.ajdecon.org. Though as the address indicates, I run that server myself for fun, so the reliability may be spotty.
I almost always ignore LinkedIn messages, by the way. If I haven’t replied to you, I probably never will — best to try email. 😉