Tips for taking better photos?

I'm really into photography and I've only been doing it for a year, just a few months ago I got my first D-SLR. It is a Nikon D3100. I have the standard kit lens 18-55mm VR and a Tamron zoon 18-270mm VR. I also have two filters, a polarizing one and a UV filter (I'm into landscapes). What are some things I could improve with to build my skills? I think I need to work on my composition, but I would like to hear your opinion. I have 2 flickr photostreams. I'll link them both so if you are interested you can look through my photos and give any feedback you might have.

Tips?

- Be more selective. A flickr site is a showcase. Not many people are interested in 30 shots of the same car in the same landscape
- Get your exposure right
- Tilting your camera hardly ever adds something
- Start reading on composition