You can advertise your work every 15 minutes in chat;
http://www.planetminecraft.com/chat/

You can post skins you create here;
recognized-show-everyone-your-awesome-skins-t14152.html

Make sure that all content you post is 100% made by you.

If you're making skins never use Novaskin, Minershoes or Skincraft. Using parts from the armoury (or any parts you did not create) will earn yourself a hefty ban.

Well firstly lol that was one question, And upload things that are unique, hundreds of skins and maps get updated and uploaded each day So it is unlikely that you will be noticed by those unless they are really unique and good, and if you regularly upload them. Try making some forum posts and getting known that way, More comments, More posts, More questions = More subscribers, Then upload things like skins, Mods, texturepacks and your subscribers will see them as well as others, That's one way of getting out there. I do it by modding and posting, Seems to work for me.

If that doesn't work get a youtube :p And link people to your PMC via youtube

Keep making good content, and you will get noticed. Its that simple.