I'm not an advertising robot creep, I swear! Sometimes I feel that a user and I could talk at length about paleo-related things but could spare the community from a really really long thread.
Some users will have contact information in their profiles (which you can see by clicking on their user name in any of their questions or answers.) If you want to contact someone who doesn't have contact information you could leave a comment on one of their questions or answers saying you'd like to be contacted by them if they're willing. In that case, you might want to include your contact information in your profile.
Consider that some people like to remain anonymous.