1. Sex (a.k.a. Physical/Biological/Anatomical Sex)
Sex is a fact about people's bodies. It's not about how you feel, but the nature of the body you're in. That doesn't mean it's always straightforward, but in my case, I don't think I can get around the fact that my sex is male. I have a penis. (Yes, it's rude to ask people about their genitals. No, I don't mind - as long as you're just curious and not looking for a reason to discriminate against me. I'm a nude model on the internet; I make no effort to hide what's in my pants/under my skirt). I suspect that I may have low testosterone, as I possess some feminine characteristics, but I still basically have a man's body - broad shoulders, narrow hips, and large feet (I say that because it's impossible to find women's shoes in my size, lol).
2. Identity (a.k.a. Psychological/Mental Gender)
I identify with femininity. I don't know if that makes me a girl "inside" or what. It's hard to consider myself a "legitimate" girl when I've grown up most of my life assuming I was a boy because of my anatomy. There are some feminine things that I'll never "get" - like what the big deal is about babies, or what it feels like to have a vagina, or a period for that matter (can't say I'm missing that one). And I have some masculine hobbies - like my taste in music, for one thing. That prevents me from feeling 100% female.
And I know, few females probably feel 100% female, but when you're born that way, you get to take it for granted; the rest of us have to work for it. But I've never identified with masculinity either. I'm not macho. I'm not strong. I'm not competitive. I'm very sensitive, and soft-spoken. Maybe in a post-gender world I could just be me without worrying about labeling myself. But in this world I associate more with the female label than the male label on most days. Especially taking into consideration the next item.
3. Expression (a.k.a. Gender Presentation)
As this one is less defined by factors outside of your control, and something you can consciously manipulate, I tend to go from one end of the spectrum to the other more freely. Most of my life I've identified as cis-gendered and presented as male without a second thought - although even then there had been times when people mistook me for a girl. But more recently, as I've begun to consider possibilities alternative to the one I was born and raised into, I've been exploring my feminine side.
These days, I present as female almost exclusively (I don't go out of my way, but I do buy nearly all my clothes in the women's department, for what that's worth), albeit with the caveat that I don't dress like a drag queen (at least not most of the time)* - so often the combination of my wardrobe (girly casual) and the fact that I don't wear a lot of makeup (I've always preferred a more natural approach) means that whether I get "gendered" as male or female depends a lot on random factors (which, unfortunately, makes the issue of choosing a public restroom even more stressful for me).
It's worth mentioning, however, that masculine visual cues do nothing for me, and I derive great pleasure from dressing myself up and seeing myself (in the mirror) as female.
*Not that I wouldn't enjoy going all "femme fatale", but ironically the more feminine outfits I own tend to emphasize the parts of me that are obviously not female. A man can absolutely wear a slinky dress, but it's not going to accentuate his bust and hips so much as his shoulders and the bulge in his crotch...
4. Attraction (a.k.a. Sexual/Romantic Orientation)
My sexual orientation is a whole lot more straightforward than my gender, or even my sex (because there is some hormonal ambiguity, and I can actually pull off being mistaken for a woman while nude, under the right circumstances). However, it's hard for me to label, because most of the terms we have for sexual orientation presuppose the subject as well as the target's sex/gender (depending on what you're going by).
Simply put, I'm attracted to girls. Very much. I'm tolerant, and open-minded, and willing to experiment if the right person came along; but I also have strong preferences, and it would be doing a disservice (to me, as well as to anyone who hits on me - including the scores of gay/bi-curious guys that I'm just not that into) not to acknowledge them.
If I had to choose a label, I'd pick "gynesexual" (attracted to females or femaleness), because calling myself "straight" doesn't accurately reflect my non-traditional gender (or my orientation when I'm passing as female), and I don't think I'd qualify for the official designation of "lesbian" (especially with that big ol' "M" on my ID). "Attracted to girls" is really the best way to put it - it says everything it needs to say, and nothing more - but you'll notice that that's never an option.
Note: Some people make a distinction between sexual and romantic attraction, but for me they're pretty well-aligned, so it's not a big deal. If anything, I might be more inclined to have a purely physical experience with a guy (if he's beautiful enough) as a form of "experimentation", but I have very little interest (even some aversion) to the idea of romance with one.
Similarly, some people make a distinction between the sex and the gender they're attracted to (often indicating that one isn't as important as the other). Again, my preferences are aligned, as I prefer the female sex and gender. I'm not trying to be exclusionary - these are just my preferences. I've seen attractive transwomen (and I'm not afraid to admit it), and I wouldn't discriminate against someone on account of their anatomy (preference or not, penises are very user-friendly).
But I, personally, enjoy the sexual coupling of penises with vaginas - and I happen to have a penis. That doesn't make me intolerant. If I had a vagina myself, it's possible that I'd be more interested in penises. I guess you could say that I'm sexually straight and romantically gay (since the idea of a woman-woman relationship appeals to me). Which is why the perfect setup for me would be a relationship with a girly girl who's attracted to girly boys with penises. But "perfect" is a huge word, and encompasses all kinds of niggling stipulations.