Don't know if you were going for that yellowish look or not. I'll assume not.
WHITE BALANCE!
Female shot is best. However, I think you cropped it too close. It appears the focus on the eyes is just off a bit. Looks like the focus is sharper on the hair. You wanna get those eyes is sharpest focus on a portrait like this. I'm not a big fan of her expression (or lack there of). I know that is really subjective, but I just feel having her do something other than being expressionless is much better--looking at the camera, rather than toward the ground would be better as well. Highlights on her cheek seem to be a bit blown out. You did use a fill flash didn't you (looks like it from the highlights in her eyes)? Necklace is probably too bright for this shot. Another necklace with a warmer color would do well.
Male shot looks too stiff. I think having him turn his head so drastically to the side detracts from the shot. This shot looks like he's practicing his alignment to his left in a military formation. Also for a shot showing that much of the upper torso, you really shouldn't cut off the top of the head. The sidewalk behind him needs to go--if it's not germaine to the shot it really shouldn't be there. Watch your background. His shirt is all bunched up.
In both cases the people look like they have indigestion. It is almost always a bad idea to have the head turned the same general direction as the torso. The photograph of the young lady would have been improved immensely by having her rotate her head slightly and make eye contact with the viewer. Add a pleasant expression to that equation and you have the beginning of a nice portrait. The horizon line isn't a huge problem in the one with the girl but it becomes one in the portrait of the boy. Be as careful in your selection of a background as you are in the selection of a location. Next, these are completely unretouched, which is usually a problem. In the digital age retouching is so simple. It isn't like it was ten years ago when it cost upwards of $6.00 per head for retouching. It is so simple now that no photograph should ever go out that isn't retouched unless there is a reason for it not to be. Time of day is also an issue in that it is creating harsh shadows. It would have been to your benefit to select a time of day or location that would place the subject in softer light. Consider joining a portrait professional photographers organization so they can teach some basic posing techniques if you are considering doing more portrait work.
Nathan: they were retouched. if i should you the examples you would see a big difference! i took off most of the blemishes i could without making it look fake. i really didn't want to do that though because why hide who you are? everybody has imperfection, instead of hiding it don't worry about it, its what makes us individuals. think for the info about posing though! im just starting out with portraits and don't really know what to do. the bottom one is a self portrait and i have no clue what im doing, most of the ones of me are accidents lol.
Mike:i was going for that yellowish look. i always keep a 50% grey card in my camera case and always shoot in custom white balance. here lately ive been liking the soft toned cross processed vintage indie feel photos, so i started to try them out. its all personal preference i suppose. about the dressing....she didn't dress to take portraits, but i got bored to doing landscapes and self so i just started to shoot her lol. i think i used the flash on this one, like you say, you can see it in the highlights of her eyes. about the self portrait, i know what you mean about the sidewalk. i kept on trying to get it out of the frame but its was hard because if i didn't have that in the frame i would have had this ugly road and trailer home. thanks for the information on posing though. like i said, have no clue what im doing when it comes to that. and the wind was super that day, and to get the light on me "right" i had to stand where the wind was blowing like that.