Looks great Lien!
For close-ups, I have a couple of tips that you might find useful in the future. First of all, use a tripod and a cable release is you have one, or use the camera's timer so that you don't bump the camera when you take the picture. (I'm not suggesting that there was any camera-shake problem in your photos above, they look great

) .
Then, set your camera to Aperture Priority Mode (on my Canon, it's "Av" on the dial). This means that you decide what aperture to use, and the camera will automatically set everything else. Select an aperture with a higher number... such as f16 or higher. This will probably make the shutter speed so slow that it would be impossible to hand-hold your camera anyway.
Using an aperture with a higher number (which is a smaller hole) will increase the depth of field in your photo... that is, more of the objects behind and in front of the point that you're focused on will appear to be in focus. The affect is stronger behind your focal plane than in front.
The idea here is that if you use the lense's maximum aperture (f2.8) the depth in your photo that appears to be in focus will be VERY thin, especially in a close up.... but at smaller aperture, f16, f22... etc) the depth that appears to be in focus will be much greater. The only thing to keep in mind is that your lens is also the sharpest (highest resolution) towards the middle of it's aperture range... so you might want to avoid the very smallest aperture that it has.
Hope that makes sense
- Matthew Gore