All too often I've heard of Game Masters who like to rough up the characters and create worlds where in the monsters seem to be all powerful, and everyone the characters meet are super-powerful wizards, paladins, and thieves. Not likely to be the case in any good game. If we consider that 99% of the normal population has no level or class, and are just plain simple folk then we gain a greater sense of heroism for the characters.

 Remember, just because it's a fantasy world doesn't mean the local baron is a 19th lvl fighter and his staff wizard can split planets. On the same token do not put magic item stores anywhere, no-one would be dumb enough to build such a store and they certainly wouldn't sell said items to anyone. Magic should be as rare as you can make it without keeping the PC's on a never ending search for the simplest of magic. An easy rule of thumb would be that PC's ranging in level from 1-4 shouldn't have weapons above +2 and no magic items that don't approximate the level range, PC's of levels 5-9 shouldn't have any over +3, and PC's of 10+ could gain certain higher powered items only at great peril to themselves. Wizards should be kept on a tight leash, here put only a limited number of high power magic-users in the world as a whole, for instance, start with 10th level and add 1-8 (d8) levels to a number of wizards equal to the number of schools of magic. This will keep the problem of too many wizards to minimum, also remember that each of these wizards will only have 1-4(d4) apprentices at any given time, so PC spell-casters must fit in this range as apprentices. non-wizard magic-users (bards, dual-classed, special characters, etc.) should also be rare indeed, or at the least their access to magic should be scarce at best. Wizards after all try to keep such arcane knowledge to themselves.

 Of fighters, even though the town has a constabulary doesn't mean they are good at it. Remember it is a 'medi-evil' fantasy game after all. The average ranks would be then, 0-level, the veterans might be 1st - 2nd, the watch sargeant might be third level with a group of some 20 watch men under him. A watch captain might be 4th - 5th level with a command over 4-8 sargeants, the chief constable might only be 6th+ level with a number of captains under him that would ensure that an average of 2 watchmen are present for every 30 people in the town.

 Rangers would be very rare, consider that just one needs a 50 mile area for to watch over then the population of them is quite small, if you consider that they are best found in frontier areas then for NPC rangers allow a level range of 1-5 for most encounters with them, higher level types should be kept to a minimum as they need more territory as they get higher in level. With these examples in mind then your game world will begin to take on a more realistic feel and the players interested in playing as they can then be heroic without fear of everyone trying to kill them.