


*disclaimer* - These are my personal observations, intended only to help newcomers to manga find their bearings and become accustomed to the new world of comic they are discovering. I am in no way claiming these statements to be iron-clad nor infallible, nor do I claim to know everything there is to know about either genre of comics. Thank you, that is all.
The first and probably most notable difference between anime and manga is the anatomy of the characters.
-Think of Superman for instance. He's built like a body-builder: square jaw, enormously wide shoulders and broad chest. He's got muscles the size of your car. The man is huge. Now compare him to say, Ranma from "Ranma 1/2" or Tuxedo Mask from "Sailor Moon". As you would have noticed had you actually looked these charaters up, the anime guys will tend to be much leaner and more bishonen, or "bishie". They tend to have rounded or effeminate facial shapes and large eyes. They usually don't have the super broad chest or shoulders, (possibly because people tend to be somewhat physically smaller in Japan than in the overfed US?) Some artists exagerate this, purposely portraying male characters as extremely feminine or female characters as masculine. Female characters tend to be very small and whispy and for some odd reason are often several years younger than their male counterparts, or at the very least look as if they are. They tend to look either preadolescent or very... developed. Manga girls also have the odd tendency to wear short skirts at every opportunity. Gag Characters are also very common, usually with large circular lips that their eyes barely peek over.
Another major difference between the styles is the way characters are presented.
In manga, you will typically see a lot of fuku-clad school girls, a lot of "bad boy" school boys, a few swirly-glasses wearing nerdy types, a lot of super powers with floating rose petals in the background. Sure there's some spandex and some gun-toting in select manga, even the occasional stereotypical superhero, but these are much less prevelant in manga. Most female characters will be either presented as cute and bubbly, sad and whispy, evil and shrill, or just tough and bitchy. Most male characters will be presented as tough, sensitive, evil, or very, very emo (aka, sad).
By contrast, in American comics, most female characters are presented as fairly normal if with extremely exaggerated proportions. Most have the attitude of your typical New Yorker, tough, edgy, and loud, and tend to wear lingerie in public for no apparant reason. (Google "White Queen" or "Ema Frost" and see what I mean.)
A third difference is in the clothing of the characters.
While your typical female American comic character will wear tight low-cut everything, often in spandex or leather, your typical manga girl will more often be seen either be seen wearing a simple school uniform or sweater and skirt, or the most complicated, ruffle-laden, strap-covered, humongous-bow-littered creations to emerge since Project Runway. These ensembles are often hoplessly complex, for no apparant reason whatsoever, and would be just about impossible to actually get into. They also often manage to expose quite a bit of skin and often a character's underwear, despite the amount of fabric the character is actually wearing. Also popular is the occasional kimono, highly prevelant in time travel-based manga, or those set completely in Feudal Japan.
Male American comic characters tend to either dress like metrosexuals in the very latest fashion with their designer sunglasses and occasional leather trenchcoats, or find interesting ensembles of spandex and knee-high boots. Male manga characters tend to either wear school uniforms, some kind of male equivilent of the ridiculous fluttery outfits I mentioned earlier, or some kind of martial-artists uniform. As with the females, men occasionally wear traditional japanese clothing, especially in time traveling or Feudal time-period comics.
One major similarity between American comics and manga is the focus on kicking butt that is usually foregrounded.
Very few comics of either genre are without a few fight scenes, even if the comic itself is not really about fighting. Comics such as "W Juliet" for instance, are more about the characters daily lives and less about their fighting prowess, but Ito, the main character, still manages to get into a small brawl at least once an issue.
Another, somewhat odd, similarity is the total disregard for natural hair colorations.
Many maga comics completely disregard the natural selection of hair colors, opting instead for interesting shades of aquamarine, purple, pink, or blue. This is considered totally normal in the manga character's world. While it is LESS prevelant in American comics, it is certainly not unheard of. Mutants from the "X-men" comic family often have unusual hair colors, though some of them have some sort of backstory to explain these unusual pigments. "Storm", for instance has snow-white hair, despite being natively African, and "Psylocke" sports a lilac colored mane.
Another very prevelant similarity between manga and American comics is the heavy use of fan-service. Generally fan-service is centered on the female characters of a comic. Manga characters often find excuses to spontaneously take showers, have their clothing destroyed in conveniently skin-baring fashions, or just wear so little to begin with that removing their clothes is hardly necessary. The panty-shot is also a highly prevelant phenomenon in the manga world. Male characters will typically strip to the waist for fight scenes or find themselves in (carefully art-directed) compromising positions. An attractive male character tripping and landing stradeling his female counterpart is common.
While American comics generally do not employ the panty-shot, they hardly need to. Your average super heroine wears little more than spandex lingerie and thigh-high boots. Those who wear "normal" clothes typically seem to buy them several sizes too small, as they cling like Seran-wrap to every inch of skin on the character's body, particularly their breasts and backside. Similar rules apply to male characters in both manga and American comics. The major difference is that they are typically portrayed as more aggressive in the American comics. For example, they do not simply trip and land in a compromising situation. They intentionally pin their counterpart against a wall, floor or whatever is handy in order to create sexual tension. Most comics will either milk this for a moment and then have the characters seperate and go on with what they were doing, or quietly skip to the next scene during such moments, though some of the more hentai will linger for a little of the action (if not all of it).
Another very big similarity to be noted in both genres is the anti-hero character. Characters like Gambit, Cloud, Wolverine, Himura Kenshin, occasionally Sesshomaru, Tasuki, Gene Starwind, Vegeta, Batman, and Black Canary, among others are good examples.