Marlin,
There are numerous recipes on-line for this.
Here's the recipe I started with, but have "tweaked" to my taste.
I'd make it as written and then make it your own.

HOMEMADE KAHLUA  

3 c. sugar
1 qt. water
10 to 12 tsp. instant coffee
3 c. vodka (buy most inexpensive)
3 tsp. vanilla

Simmer sugar, water and coffee for 1 1/2 hours. Cool and add vodka and vanilla. Put in bottle. Ready to drink, but will get better with age. OR:

2 c. water
3 1/2 c. sugar
2 tsp. vanilla
1/5 inexpensive vodka
6 tbsp. freeze dried coffee

Boil water in large pot, add 3 1/2 cups sugar and boil 5 minutes. Add vanilla. Dissolve coffee in 1/2 cup water and add to pot. Pour in vodka. Makes 2 fifths. This needs to age at least one month.

I changed the instant coffee to the equivalent liquid in my choice of drip coffee, Folgers Supreme. I also cut back the sugar by half. You just mix to dissolve sugar and bottle. The biggest "tweak", is I substituted a white rum for the cheap vodka. Even cheap white rum is aged longer than cheap vodka. I believe it makes a smoother finished product.

Another item I will bring instead of the Home made Kahlua, is a mix of Wild Turkey and a store bought Mexican coffee liquor, which is much cheaper than the Kahlua brand. I fill a 1 liter square Naglene bottle with the Wild Turkey, and top off with coffee liquor. More punch than Kahlua, but smooth in coffee or hot cocoa ;)