Looks:
General: snakepeaple, human upper body and snake lower body, the human part is abaut the same scale as an ordimary human (males 5% something larger, females 15% larger than the males so 30%-ish larger than human females?), the snake part is about 3-4 times as long. the humanlike skin passes abruptly into the more snakelike skin at waist height, this line forms a V shape at the front and is more smooth at the back.
Colouration: the skin on the upper body is usually a light brown shade similar to humans at medium warm climates, however the match is not exact, and the texture is different, some also have barly visible darker stripes on various parts of the body, these are generally considered a positive look. They have a different set of skin imperfections and disorders than humans. Their hair is always black, white, or some grey in between, usually black. The snakelike skin varies between all kinds of browns and greens, and there are many different patterns, however the patterns generally variates the colour little and high contrast patters are very rare.
Head: the gender differences are less than human (so females would look more masculine and males more feminine), their hair is usually long and untended to, they have fangs, but despite what one would belive these are not like those of a snake but more lake a carnivorous mammal. the eyes are snakelike and wider than human. (as in the visible part, still spherical so technically that should be just "larger" not "wider") They have a long tongue, about 50cm, similar to that of a giraffe.
They tend to smile and laugh a lot, enough that a smile borders on being countable as a permanent feture, making those fangs visible to an amount that might unsettle some races...
Torso/arms(humanlike part): Larger and more muscular than human, they are hardy and powerful in build and about 190% as strong as an human of the same physical fitness. Their fingernails are thick, narrow, opaque, and pointy, but not exactly claws. the skin is leathery and scales actually begin already at shoulder level and are simply covered beneath the skin until the V line. their inner anatomy is mostly similar to a snake and not human, meaning that the torso contains really no vital organs, this has lead to stories abaut them surviving having their heart and lungs pierced by spears and arrows when in fact those spears and arrows missed by several meters. the stomach really only contain muscles and some parts of digestion, two large muscles near the surface leads to both that they will never have a "six pack" look, and to the indention often mistaken for a stretched out navel.
lower body/tail(snakelike part): about as muscular as any snake of the same scale (meaning a lot), this part also contains the majority of internal organs. the scales are long and thin and similar to flat needles or spikes, leading to sometimes looking almost like fur. The crossection of the body is slightly triangle shaped. This part of the body contain most vital organs, underneath scales and thick skin providing almost as good protection as metal armour.
Biochemistry/eating habits/population growth: Being snakpeaple, one would wonder if they are mammals or reptiles?
There is an obvious middle way.They lay leathery eggs that hatch after about 3-5 months, these eggs have a leathery skin and are huge (40cm*40cm*60cm), they are laid one at a time and whit 5-30 years in between, how many young a mother chose to have varies roughly among the same numbers as humans, but generally far to the lower end of that scale. they reach maturity at abaut 30-40 years of age but usually waits whit getting children until at least 100 (compared to human 18 maturity 30 for children or so?), average lifespan is 200-300 years but the maximum around 400-600, some rare (1/10000 of the born?) might live arbitrary long due to magic gifts.
They are omnivores, but have a hard time digesting food whit large amounts of longer carbohydrates like bread, they cannot digest starch. Generally they eat meat and fruit but they also love sweets. They are cold blooded and thus need little food compared to if they were not, and can even go months without. due to their size and activity they still need several times as much as a human thou.
Culture/technology: Think ancient Polynesian, flowers and hula dancing and merrymaking taking up whatevr part of the time not spent on getting food. Religion-wise, they aknowlage gods but do not worship them, they are instead mostly shamanistic and many have gifts that alow them to comute whit varius spirits.
They do not have any central rulers, not even tribal chiefs, nor any designated shamans, in fact they do not have the concept of set social positions at all. They make decisions in a disorderly collective fashion similar to an anthill, the strongest single factor is probably the advice of elders generally known to be giving good advice.
Technology wise, their knowledge is mostly at bronzeage level, however, they do not keep fire and thus does not use metalworking. They rarely farm in the way humans do, but frequently keep vast orchards, they sometimes breed cattle but it has a tendency to escape as they do not do selective breeding and consider fences cruel (not that they care much about animal rights otherwise, but they really hate fences and walls). They do not plan their buildings and as such cant be said to have architecture, however they do have a good sense of stability and sometimes their structures can be impressive.
They do not use clothing as such due to the warm climate were they usualy live, however they do use rather large pieces of colourful cloth jewellery ((to me, a tie is jewellery, as it serves no practical function)), and generaly wear flowers, huge contraptions from flowers, that hopefully cover everything from your minds eye.
They are good at mechanics, but limited by using almost exclusively wood, they are also highly skilled at most forms of weaving, be it silken cloth or baskets or ropes. The idea haven't stricken them to use catapult or similar in war, but one exposed to the idea from outside sources they might be adept at it as long as the scale keeps small enough for it to be a one man project.
They rarely or never weapons or armour and don't have the concepts really clear, they might put a rope whit rocks around their fingers to strike harder, but something like a sword they would not know what to do whit at all. if presented whit armour they'd probably classify it as protective jewellery and only wear it if it also looked nice.
Tactics: They are a peaceful people and does not even have a word for war, however they are not completely unfamiliar whit the concept and some traditions to remember it are maintained.
If attacking, they will use the same tactics as hunting: sneaking up and ten attacking wildly. Their fighting style is berserker-ish and they punch, bite, and crush foes whit their powerful bodies, there is no such thing as military training but their instincts usually guide them well, and one unarmed could easily beat 2-3 humans whit swords and chain mail, and still have a decent chance against 15 such humans if having the element of surprise, their style is beast like and chaotic, and they often does not kill their foes but instead maim and knock out and kill people randomly, they are terrible to behold and can wreak total havoc even on well trained troops. However, they are quite a bit less efficient against mounted combatants, and against ranged opponents or advanced tactics they have no real counter at all except their tough scales. They have no ranged weapons, if they cant get to a foe because of some obstacle in between they might throw rocks, but that's about it.