I always love this question and the answers it brings. I actually grew up in a small town in the mid-west (pop 350), so lets look at this froma real world perspective and then go from there.
First you need a reasource - farms, mines, fishing, logging, ranching...something that is going to be the reason for this community in the first place. This will be the tie that binds the whole thing together. I will use farms from now in in examples, but its all pretty interchangeable.
Secondly, how long has it been here and is it growing shrinking or staying the same. Is this a burgeoning little village on its way to becoming a megaopolis (ie colonial Boston) or is it a failed attempt at greatness fueled by rumors of hidden treasures (ie colonial Jamestown). Or maybe just a location where someone settled and that's where they stayed (like my hometown of Alto Pass, Illinois) not really concerned with growth, just survival.
Next what does the town need. Our farming village needs a well and a few services related to the industry which it supports, a blacksmith, a wagon wright or wheel wright, and carpenter. These things are an absolute must. Farmers can pretty much make or grow everything else, but tools are required and making those is a specialized skill. Your blacksmith will be skilled in making knives and such for day to day lving and your carpenter may be able to craft wooden dishes as well. Even though this may be a small village, these three people are uber craftsmen. Not bent on greatness, but survival of their trade. Being able to craft the finest sword in all the land may be on the mind of a blacksmith in a city where such notariety will gain them business, but out in the middle of nowhere a well crafted plow, beats a well crafted shield. Just something to consider.
As for the comment on alcohol. Local moonshine might be available, but may not be for sale. (plot device?) Caravans are probably the only source of trade goods (crops for items) and bards would be the only source of entertainment (a bard would proabaly end up being somewhat of a local celebrity if they stay around).
As for law enforcement, an established constable may not exist but a posse of pitchforks and crude wooden spears would likely dispatch any lawbreakers fairly quickly. Think Salem witch trials or old west law. I've actually seen a posse deputized in my youth and they are quite effective at reigning in lawbreakers. (as a couple of city folk from Chicago who escaped from a state prison found out)
A church and a cemetary are absolutely required. People that stay is small towns are usually bound by some unspoken moral code of never severing the ties you have forged. The term conservative in modern venacular describes the solid, old fashioned thinking of most farm folk. Not superstitious (although you'll have a few of those) or stupid, though certainly there are a few of those as well, just slower to act because reprocutions are more long lasting when every action you make usually concerns your very existance. For a good literary example of this read the first couple of chapters of "The Wheel of Time" by Robert Jordan. I realize there are a lot of opions on Mr Jordan's work, but I have to admit that the section of the Two Rivers folk are dead on accurate and a great peek in to small town life.
Now, what will your adventures need? A place to stay is obviously a must. While an inn would be nice, how about a boarding house? Farmers are notorious for renting out their extra space for a few coins to supplement their seasonal income. (How do you think bed and breakfasts came in to demand?) It is possible that the party might not even stay together at a central location, but be boarded at several differnt residences. Of course if they need to, a barn might end up being their only option as a local Holiday Inn.
As for livestock (ie mounts) farmers will be hard pressed to part with their livery but the right application of shiny metal discs (ie coins) may bag quite a bargain. Of course these animals will not be trained in war, so using them in battle might get a little dicey, but strictly using them to get from A to B is probably ok.
Provisioning should be easy as nearly everyon can either make or sell for a bargain the normal items the party will need, rope, leathergoods, candles, torches and the liks will proably be had at a fraction of the cost of these item in a city. However, this will quickly be balanced by the general lack of arms and armor. A family may own a suit of chain, but it will be an heirlom handed down from generation to generation from Great Grandpa Dave who wore it during the war... They will not part with it except for LARGE sums of gold, the sentimental value is far too great. The blacksmith could fashion some weapons, but he would have to stop his normal well paying job of making nails, horseshoes and candle holders to craft a few crude weapons for what is probably a once or twice in a lifetime opportunity. Financially, it doesn't make sense to spend time on one expensive item, so the cost to get him to do it will be great. But there could be an exception...
If your farmers suppliment their diet with meat, there is probably a local huntsman who is also an accomplished bowyer/fletcher who would jump at the chance to sell his extra gear or even teach someone the craft outside of the hunting season. Because of the normal need of arrow tips, the blacksmith may have a normal "production run" of these which would be easy to increase in number at no lose to him. So arrows and bolts, might be readily available after a week or two.
Of course we are in a fantasy world so lets explore a couple of other options, the local elvish or dwarvish communities. (Or gnomes, halflings, goblins, or even humans) Trade among local communities is going to happen if there is one nearby (ie three to twenty miles). Local towns trade non-common commodities (ie crops for fish or fish for ore) in order to get what they need in return for what the have. If you go with a farming community make a couple of nearby towns that are similar in structure but have different commodities (ranching, mining, logging etc) so that there is a source of non-available goods. You don't need to flesh out completely, just a list of trade goods and maybe a local trader NPC from that town. Of course this allows you to have growth options for your campaign as well. (I heard that in Haverville that they have been losing horses to goblin raids.)
Sorry for the long post and this is by far not definitive. Hopefully this helps, just my two coppers. Happy Gaming!