In regards to your Question, like in real life, most people are busy, have preferences, and are somewhat still new in getting into the world of Internet matchmaking. This Topic has been discussed before in the Forums and some of the take-aways are;
Make your message or Emo personalized, be friendly in your approach, have more than 1-2 pics in your profile, try and fill it out as much as possible, and then get involved in the Forums and get to know more of the 'active' users.
Hope this helps.
I will always respond (at least try) if someone sends me a message. An emote without a comment, not so much.
Honestly, I can't answer that one. I have the same issue. I try to have the mindset that if someone doesn't respond, it is their loss. It can be frustrating, but the right person will come along and respond. So don't give up. If you figure out the trick to getting responses, post it in the forums. I am sure others would appreciate it!