This is how I go about making guacamole for 2-3 people.

Ingredients:
2 Avocados
2 Tomatoes
1 Lime
1 Clove Garlic
1 Bunch Green Onions
2 Jalapeño Peppers (you can use less if you like it milder).

You also need a bowl/storage container for mixing/serving.

Step 1: Create Base

Cut lime in half and juice into the bowl.
Dice tomato and remove seeds and add to bowl.
Finely chop the green onion and add to bowl.
Mince garlic and add to bowl.

Mix ingredients in the bowl.

Step 2: Cut Avacados

Cut the avocados into cubes
Cut the jalapeño peppers into small cubes

Here's a nice trick for the avocados.
Cut an avocado in half and remove seed.
Cut a grid in each half
Invert half and you are left with avocado cubes.

Step 3: Add Avocado and Peppers to Bowl.

Add the Avocado to the bowl.
Add the Peppers to the bowl.

Step 4: Mix and Sit

Mix it all together.
For best results, let sit for 30 minutes to an hour before serving (the flavors have to mix).
I usually put the avocado seeds/pits back in because I have heard that it prolongs the browning process. I don't know if I believe it, but it kind of looks cool so I do it.

Variations:
More Heat: Add some cayenne pepper
More Traditional: Add cilantro
Less Mushy: Mash avocado first and fold in other ingredients