Rule of thirds in a nutshell:
Place a pretend tic-tac-toe grid on the screen you're looking at and use it to compose. NEVER put anything half/half (half sky-half beach/water for example). Instead put the vertical 1/3-2/3 (for instance, the beach/water might use up 2/3 of your screen and the sky only 1/3). Don't put people's faces dead in the middle of a shot... make it the upper 1/3.
Try here for real detail about it:
Rule of Thirds
Or here for more info on general composition:
Kodak Site
As for you pictures other than that... the first picture would be absolutely beautiful if it weren't out of focus. Check you camera for the minimum focus distance and whether or not it has a macro setting for close up (macro) photography.
The second picture is also out of focus.
The third picture is focused nicely but the obsturctions in the foreground distract the viewer from the bird, which I presume is the main subject.
You may want to hang out at the forums over at
DP Review to get more expertise.
Take care and just KEEP SHOOTING! The masterpieces are there waiting!
Joe