Step 1: Schedule the tasting for mid-afternoon or mid-evening.
You want it to be after people have eaten and feel satisfied, but before they actually feel hungry for the next meal.
Step 2: Choose your guests.
A small group of 6-8 is best for interaction and for costs. Invite people who are interested in savoring food, rather than just gobbling it up. People who like wine are more likely to enjoy a chocolate party.
Step 3: Choose your menu.
There are many different kinds of chocolate to choose from. Select a few different kinds of chocolate you have never had.
You can select organic and fair trade chocolates, and talk to your guests about how chocolate is made and how the cocao industry works.
For a fun twist, throw in some chocolates that are made with sheep's milk or goat's milk. There are also chocolates made with chiles, fig, bread, and curry.
You can also expose your guests to chocolates with a much lower sugar content than they're used to. At first, it'll seem bitter, but challenge them to notice flavors that would otherwise be overshadowed by sweetness.
Another potential theme is choosing chocolates that are made in your region, if there are enough. Look in the closest city with a chocolate shop or chocolatier.
Step 4: Purchase enough chocolate for everyone to taste.
There should be enough for each of your guests to have two squares of every bar. Remember that this is a chocolate tasting party, not a chocolate eating party.
Step 5: Create a sheet for notes.
It should look like a spreadsheet, with columns for aroma, flavor, texture, finish, and the chocolates you've chosen listed on the left. Make copies and have them ready for your guests, along with pens or pencils.
If you want to encourage people to mingle, put the chocolates in a different numeric order for each sheet, so you have, say, two random people at one chocolate at any given time.
If some chocolates are sweeter than others, be sure to have your guests taste the sweetest ones last.
Step 6: Set up a table with each chocolate on its own plate.
Break up the chocolate into pieces along the lines etched into the bar.
If you want to be extra fancy, stack them up like a little pyramid.
Be sure people have a way to know which chocolate they're tasting, such as by having an unopened bar next to the plate. If, however, you don't want your guests to know which chocolate they're tasting - like if you don't want their perceptions of a certain brand to taint their opinion, or you want to see if people taste the difference in organic or sheep's milk chocolate, use generic labels like "Chocolate 1" and reveal what they are later.
Step 7: Provide a palate cleanser, such as plain bread or crackers.
Also provide water and napkins.
Step 8: Give everyone a brief talk about how to taste chocolate consciously and deliberately. (see "Steps to chocolate tasting" below)
Step 9: At the end of the party, ask everyone what their favorite chocolates were and why.

Steps to chocolate tasting:

1. Find a location free from background noise and smell, such as television, music, a crying baby, road traffic noise, talkative friends, etc.
2. Clear your palate.
3. Make sure that the piece of chocolate is large enough to accommodate full evolution of the flavor profile.
4. Allow the chocolate to rest at room temperature before tasting.
5. Look at the chocolate.
6. Break the piece in half.
7. Smell the chocolate, especially at the break point.
8. Place the chocolate on the tongue, and allow it to arrive at body temperature.
9. Observe the taste and texture.