Pick a place where you are going to have your party at.
Step2
Determine a date/time for your party.
Step3
It doesn't have to cost you much at all, just decide what you want.
Step4
Find a date, if it's that kind of party.
Step5
Start picking the people. Only invite guests that you want.
Step6
Make invites or buy them.
Step7
Pick the kind of food you want for your party.
Step8
Pick out the kind of music you want for your party.
Step9
Have everything for your party -- your house and yourself.
Tips & Warnings
Consider a theme for your party. It is easier to plan that way.
Always show up at the place of the party 2 and a half hours before the party starts to take care of decorations, cake, drinks, food, music, etc. Make sure that everything is perfect.
Play it safe: Remember, if you provide the booze, you provide the transportation (or at least make sure they've got safe transport).