Do you reply to all of your comments, some of your comment or none of your comments? I am of the mindset that it would be rude NOT to reply, but feel like if someone's just saying "cute kid," they probably don't expect a reply.
Which brings us to my second thought, do you reply by email or in the comment section of your blog?
I try to reply to everyone but I do it on my blog within said post. I also go to their site and see if they have a topic I could jump in on and when I leave a post I tell them thanks for stopping by my blog :-)
I try to make a comment back on their blog. I feel like if they took the time to comment on my blog it is nice to do the same back. I am sure I miss some, but do my best. I don't usually go back to their blog to see if they commented w/ in their blog. I think everyone does things a bit differently.
I am not sure about this one yet? Do people go back and read if you have replied? Which implies maybe emailing a reply is better?
I sort of do a mix of both at the moment!
On blogger there is a box that your commenter can click to have responses emailed to them. I always click that box on others blogs so I can continue to follow the discussion and read the author's responses.