I dunno.
Don't take this the wrong way, since I am just trying to be honest here, but I always get friend zoned. (Incidentally, that's the way I like it. Though for awhile, my neighbor lady was really laying it on thick.) I really don't care too much about how I look, since I am not terribly interested in a hookup anyway, and am not looking to advertise to begin with. But, if being aloof and eminating an aura of "unconcerned", was attractive, i'd probably have had more offers.
Just from looking and talking with people of that pursuasion, mostly, they are more interested in a well developed and confident personality that is dependable and not clingy. Being friend zoned has advantages (for me anyway) because I can overhear and even pitch in on such girl talk conversations. From what I've overheard, many chicks dig a guy who's helpful and handy around the house, and some seem to really enjoy watching men work. Beats me how seeing somebody get dirt and sweat all over can be in any way attractive, but then again, I don't experience it regardless, so the whole affair is a grand mystery to me.
The real thing is to avoid having or being a turnoff. Don't try to pick girls up, but you can drop a flattering compliment and a knowing smile. Women tend toward being quite good at noticing such things, and enjoy being noticed, as long as the attention isn't "entrapping" or "disgusting"/"offensive". Just like folks hate a pushy salesman, I get the impression that women really don't like a pushy dude trying to pick them up. Once you become a turn off, that's it, game over bro. Likewise, don't play the niceguy. Be just a little bit forward, but not vulgar about it. Eg, you see little miss hotty in the black dress, surrounded by her girl wall? Just unabashedly say something like "I like it!" And give a thumbs up as they sail past. Nothing more needs to be said or done. If she's interested, she and her girl wall will gossip about it awhile, then come find you to learn more. Otherwise, you already played your hand, and did so in a way that may well have made her night more enjoyable, and that's something to feel good about all by itself. Rest assured, girls talk about things like that, and if they liked the attention, it may well bear fruit of some kind days or even weeks later in unexpected ways. Just don't worry about it. The world isn't gonna end if a compliment doesn't get returned. Just dial back the hormones, and have a good time. That IS what you go to clubs and such for right? Because if you go to such places to score, you are going for the wrong reasons. You really don't want to come off as the poor lost puppy, looking to go home with somebody. You know, "desperate."
It is very important to remember that women go out with friends to have a good time, and wear attractive clothes and makeup just to feel good. They may or may not actually be advertising or even realy looking. To know if they are or not, you have to get good at reading body language, or become psychic. Sorry, them's the breaks. Doesn't matter anyway. You and your friends should be going out to have fun too. The best chemistry happens when there's no pressure, just fun. If you and your friends can have a good time with a group of girls, and it makes your night out more enjoyable, fantastic. Otherwise, why complain? You still had a good time, right?
For the life of me, I really just don't understand the hormonal brain shutoff that many people have around the opposite sex, because those hormones? They make you act reeeaaal dumb. LOL. If you think somebody's hot, and the situation is appropriate, go ahead and let them know, but just don't see or think of it as some ritual to get something extra. That's entirely the wrong approach, and is the kind of incorrect goal that hormonally overpowered brains cook up. Flattering women is FUN, all by itself. Doesn't need anything else. You can make a great evening doing nothing but that. Girls have their girl gossip, and guys have their guy time, but really, the same sorts of games come out of it. Guys make games out of trying to get girls attention, and girls make games of trying to get noticed. Make a game of seeing how many pretty girls in the club you can make smile and giggle with a compliment, and keep score, just between you and your friends. That's the whole objective; make them giggle and smile as they walk passed. (Rest assured, they and their girl wall are probably doing the same thing, so don't sweat it.)
Me, I just watch this stuff go on, and laugh. Its fun watching people go through these silly activities, and how they react to different things.
Remember, even really butt ugly guys and girls can find somebody. Beauty is in the eye of the beholder, so don't sweat it if you get the "ewww! Ick!" Reaction to dropping the flattering compliment. It just means she isn't into your kind of aesthetics. No big whoop. The world takes all kinds. (Seriously, some women really dig fat, bald, greasy men. It's their thing. Who knows why. Others like musculuar guys, or skinny tall guys, or whatever. They come in all kinds, and everyone has something at least one other person is looking for.) Don't sweat it if you get the "ick!" Reaction. Just laugh it off and move on. In fact, you can keep a score for that too with your group of guys.
That's about it on the "friendly bad advice you should probably ignore" front from me. Anything more isn't something people tend to like having other people watching, or having a 3rd wheel around, so how to handle that hot date after getting her number? Beats the hell outta me. That kinda thing's waaay outside my element.
Just stop fretting over wondering if you are attractive or not. Seriously, ever seen the phantom of the opera? Dude was burned all over. Still got the girl. Don't fret about it.