Recently I've been receiving emails asking for advice on cross-dressing (laughs)
Honestly, I'm surprised! But I'd be lying if I said I wasn't flattered....

I can't give you an exact method for how to pass for a man, but I can give you some pointers and personal anectdotes for those who are curious, or who simply want to try it out and see if you prefer being male. I personally am quite happy as a female, and when I'm not cross dressing would never be mistaken for a man, but everyone has their own preferences.
Please remember that everything here is meant as a suggestion, and that different methods will work for different people. The important thing here is to work with your natural body and face shape.

Suggestions

1. Work out
Men's bodies have different muscle and skeletal structures, the most noticeable being the collarbone and hips. However, there are other factors that play into the male frame; women, who ironically worry about their weight much more than men do on average, have an extra layer of fat over their muscles! In order to mitigate the effects of that, you really might want to try muscle toning excersizes and running. Mens leg muscles are widest at a lower point than women's leg muscles and their arms are usually more toned. However, if you are serious about working out, you can get to a more angrogenous point. You'll still be 100% female though - don't worry! I don't mean bodybuilding! (>_<) Just a few repititions every other day. It'll tone without adding muscle unless you really need muscle anyway, and in that case then it's good you did it either way.
For legs, I suggest aerobic excersize like running. I run about 5 miles every other day.
If you're naturally heavyset, still try to get some muscle definition. And none of those silly energy bars or drinks; they're all sugar. Do remember that there is such a thing as "butch", and decide if you want to be a cross-dresser, "male", or a dyke. They're quite different things.

2. Tape your Chest
I don't have much of one, so a middle schooler's sports bra works fine for me. However, you can try bandaging your chest. If you do this, it's better to move excess body quantity a little higher than just smooshing down towards your tummy. Also, try going horizontally even. That looks more natural (what guy's rib cage is wider than his chest?!).
Try minimizing your bottom too, somehow XD I can't believe I'm talking about this......

3. Get a good quality wig
I get my wigs from the Subnade wig shop in Shinjuku, which is were Vivienne Sato also goes apparently. Don't spend $100 on one, but also make sure it isn't made of plastic like the ones at the Haloween Shops. You may want to try to go for a wig that will make your face look longer, and which fits your natural face shape. Women's faces tend to be rounder than men's, so those with really round faces should see if you can find something that mitigates that.
I use the "Yon Pe" wig model. If you don't know who he is, please look him up. He is funny.

4. Make-up changes face structure
Apply light foundation/concealer/translucent powder first. You don't have to, but it'll make the rest of your make-up look a lot more even and natural.

a. Eyes - men's eyes aren't usually as round. Try making your eyes appear narrower by underlining your lower lashes in a medium-light brown eyeliner. Underlining your entire lid will only make your eyes look rounder, so do the last 1/2, and try drawing an extra line to bring the focus a bit more onto the outer part of your eyes.
Next, using a few shades of matte brown sweep eyeshadow through the crease of your eyelid and a little out past your eye to make them appear longer and narrower. As with any make-up, blend a few colors and make sure they're worked into your face to look natural. You can add eyeliner to the upper lid if it's more convincing, but no mascherra. Depending on your eye, you may have to use eyeshadow along the entire crease, or maybe only on the outer 1/2.
Finally, put a little white on your brow bone just at the end of your eyebrow and blend in. This doesn't make you more guyish, but it does make you prettier.

b. Eyebrows - pluck all stray hairs. chose a shade of eyebrow pencil only slightly darker than your natural color/wig color and draw your eyebrows a little heavier on the inside, shortening the space between your eye and eyebrow. Go less for an arched shape than an inward slanting line that gets thinner as it goes out. Don't just have a line though; do have a naturally looking brow. Unibrows are not recommended.

c. Lips - Use a natural colored lipstick (look at your friend's and father's lip colors before deciding). Don't go too natural, but no bright pinks. Work with your skin color. Also, try to make your lips a bit more squarish and less arched at the top.

d. Facial structure - with a light brown eyeshadow, you may want to try contouring/etc. Go over your jawbone on the sides of your face to try and thin your face out. This may also work well with the hollows of your cheeks.

e. Experiment! - as I said, depending on what your natural face shape is, you're going to have different features that stick out as "female." Try looking up make-up contouring online. I myself don't have any, so I've got nothing to suggest offhand.
I also know Tyra Banks went undercover as a man for a while, so you might want to see if there are any copies of that episode running around. (I sooooo don't watch the Tira Banks show! I just turned on the TV for my monthly viewing of Billy and Mandy and it was on the wrong channel due to my Dad's obsessive habit of recording Stargate and The 4400...)

5. Clothing
Naturally, chose long-sleeved shirts that hide your hips and avoid anything that shows your neck or chest too much. You've not an Adamsapple. Chose what you think will look best on you. I myself can't pull off "football player" (I weigh about 100 lbs XD), and besides, you're already wearing make-up ; ). You can though, wear, say......hm. If you've properly modified your chest you could get away with a hoodie, tank top, and basketball shorts.
But my suggestion is to go metrosexual (*lol*). Just don't wear pointy cowboy boots and Abercrombie because that's a little too over-the-top. In terms of Gothic & Lolita, cyber, punk, gothic, and oojisama are the better styles, or you could go for a "dandy" look.

By the way, baggier clothes make you look larger, so a baggy gothic shirt with long sleeves will not only bulk up your chest, but it'll look extremely cute too. Avoid tight pants, obviously.

6. Movement
Men sit, walk, and move differently from women. There's nothing more masculine than sitting with your legs out 45 degree and resting your elbows on them, as a suggestion. Watch how men walk also, and you'll see that their center of balance is located in their chest, causing them to naturally saunter a little more than women do.
I suggest finding a random male, such as a friend or parent, telling them you're going to be studying them, and then just observing how they move. I myself found some random guy and copied him, and now I'm a little "flamboyant"....well, anyhow.

7. Personality
If you know what guys are interested in and can actually "hang" with them, it'll help. So yeah. I get mistaken for a man sometimes online because of my random love of Japanese boy's cartoons and knowlege of things gay and Dada. Decide what you want to be and be it. Utena might be cool if you're going for a Prince. Nichome-ish might work better if you're going for cute younger brother.
I....no matter who or what I am, I end up a complete weirdo (laughs)...so....

8. Voice
Try not to speak XD

That's all I can offer. If you have any specific questions please email me.
Just as an explaination of my experiences, I've dressed up and scared people out of the women's bathroom in Japan.
At the lolita event I went to, some people did think I was male, but it wasn't as convincing because I was ooji-kei.
I also found a gay man who looked frighteningly like me when I do cross-dress
(he was so gay XD I could tell the moment I saw him that he was reading Patalliro~).
But everyone at the drag clubs could tell I was female, so you'll not be able to fool everyone. First off, you don't have facial hair....

You can see somewhat poor examples in the gallery, and when I find more pictures I'll post them here. I do have a really nice one I've been trying to find....I'd fall in lerve with me *lol*