Elven village restriction has to do with race and Elf kills. Raising Charisma gets you in, and having low elf kills helps.
Dwarven Stronghold restriction has to do with race, spells and money. Have little spells and lots of money.
Necropolis can be entered when you have recently died.
Draconian Lair has Drunken Guards that always hit you for around 4000-5000, so have enough life, with an Invivibility Ring.
Wearing Stat-boosting Amulets/Armor gets you in, but holding or equipping anything that is 'Red' or 'Ice' has anything to do with Dragons will keep you out. Stay away from Red Hot Chili Peppers, Red Armor, and other stuff like that if you want to get in.
Halfling Shire can be entered when you have many different kinds of food (have as many as possible, better safe then sorry).
Orc Outpost can be accessed if you sided with them in the Orcs vs Elves Quest.
Finally, all villages, inclucing Orc Outpost, can easily be entered if you equip an Invisibility Ring, bought from Halfling Shire. So basically, just get 410 Int to get to Halfling Shire, have many kinds of food to get in, but the Ring, and then you can enter all villages safely. Pixies are invisible by nature. Lucky them.
Be careful however when you enter Draconian Lair. Have at least around 5000 Life, since Drunken Guards always hit you ..