I've noticed that at least once a week someone posts "why do you all hate me?", "why does no one respond to my posts?", or some such other plaintive cry.
No one hates you. No one is delibrately ignoring you. Everyone on here is lovely, and you'll have a hard time pissing anyone off. Except Intox.
Not all threads are successful. You aren't going to get the next 15,000 reply post on your first day on the forum. Hell, there's only been one of those to date as far as I know.
Some threads may not get any replies. Frankly, that particular post just didn't pique any interest, or no one else had an opinion. Hell, I've posted a few threads and had no replies, and I like to think of myself as reasonably popular on the site. Don't take it personally.
Do you post on other people's threads? Or are you just making your own? You'll find that if you post on other threads a lot people will get to know you, and they are then more likely to look at your threads. If I see a thread entitled "cheese is great" by someone I don't know, I doubt I'll open it as it sounds dull. Could be a nobel prize worthy discourse on how cheese making could bring peace to our time, but since you've not established credibility yet I'll skip it, sorry.
Now if Peanut or Reiko or Shaggyjebus or any number of other folks posted the same thread title, I'll likely pop in to see what's gone wrong with their head. Why? Is it because I like them more than you? Is it because I hate you? No. It's because I've encountered them in other threads, or they've posted in my threads, and shown themselves to be interesting people, so I keep an eye out for them. Oh, and Peanut is my wife, so she'll always have the advantage there.
Why don't people PM you? Let's think - why don't you show up on my doorstop with a bottle of wine? Because you don't know me. Post in some threads, get a feel for the people who hold similar views, or interestingly different ones, and send out some friend requests. Chat to the people in threads some more, leave a nice friend comment. Soon they will be posting in your threads and leaving you friend comments. If you want to chat, drop them a PM. They'll probably reply. If you expect someone else to do all the legwork in forming a friendship, you'll be a little dissappointed, both on forums and in real life.
So, in summary:
If you want people to talk to you -
1. Start by posting in other people's threads. I can't stress this one enough. If you skip this step you'd better be a damned interesting person with a knack for catchy thread headings
2. Send friend requests - don't just wait for them
3. Leave nice messages on people's profiles
4. Send a couple of PMs. PMs breed replies