#1 is terrific... nice natural and interesting backdrop for a super cute subject, mid-munch to boot. For some reason, I find the out-of-focus foot more bothersome than the eye. Setting's generally look good: f/7.1 is small enough to provide some depth of field though perhaps f/8 or f/11 would have made it that touch sharper. Any smaller than that and diffraction starts to kick in. Smaller aperture means a slower shutter or higher ISO though: shutter speed was 1/500s and you were at 100mm on a 1.6x crop body (the Rebel XT has a smaller sensor than the old film format) which is equivalent to 160mm, the rule of thumb is 1/160s minimum. 1/500 is nicely safe, but 1/250s would probably be fine too... doubt he's muching that fast. And ISO400 is slow enough to avoid too much noise, but better not to go to ISO800 if you can avoid it. So, all pretty close to optimal.
An oft-quoted compositional guideline is to put subjects in a third from the edge (Rule of Thirds), but I like having him in the centre as it makes him look more static, rather than about to move away.
The "shoes and socks" sot is really good fun... the shadow cuts across usefully above the centre (might not be Rule of Thirds proportions, but could be Golden Ratio or ~1.6:1). Legs disappear diagonally towards the corners which is good. Extrapolating the knee positions certainly suggests the flexibility that's the domain of kids (and dancers perhaps).
#3 is charming, though her face seems shadowed, not only a little darker than ideal, but also the contrasts are a bit dull and some of the shadows that help clue the viewer in to the 3D curvature aren't evident. It's not a studio shot though, so can't expect "perfect" lighting, but if you're interested - the most recent post I can think of touch on the subject was Benji's here. Don't think he mentioned it explicitly, but ideally the main light will be about 45 degrees to the side/above/in-front of her. Good stuff to know, so at least you can look out for it while taking candids.
Great flowers too: combination of pink and black raises the interest levels massively, gives it some linearity too. Main thing here is the framing. Firstly, the camera's aspect ratio is pretty arbitrary: historically cameras have used other ratios and it can all work fine, so don't feel bad about cropping something squarer or into a panorama if it simply works better (unless you want to use a pre-made frame and matt), or need to fit something to a specific spot on a web site/document etc). Here, the bits that need to go are the tips of flowers at the bottom, the half flower at right, and at least the tips of the leaves at left. As is, they all attract attention and draw the eye out of the photograph. You can't always win them all though: there'll still be a flower sticking out the top, but if you're more aware of it you can minimise that next time you're framing, or you can clone it out, or soften the contrast with the other background to deemphasise it in post-processing.
Cheers, Tony
