• Organize within your lists by categories.  For events, categories might be:

• Invitations (guest list, finding invitations, write them, mail them, track RSVPs, send reminder, etc.)
• Decorations
• Prepare house (dust, do floors, clean windows, clean out fridge, get piano tuned)
• Outdoor prep (shovel out walkway, replace broken porch light)
• Activities (make music playlist, plan games)
• Supplies needed (plates, napkins, bottle opener)
• Food & drinks (subdivided into categories)

This makes it easier to work on one category at a time, to figure out what you've forgotten, and to assign tasks to others more easily.

• Keep all your lists in one place so that you can FIND them when you need them. 

• Some low-tech solutions might be a small binder that you carry in your purse, the back of a day planner, a clipboard, bulletin board, or the refrigerator 
• Some electronic locations are your computer, cell phone or other PDA
• Choose whichever type of system works for you, but be consistent with it to make it easier to remember.

• Establish a target date for each item on your list. This may be the most important key to successful time management. Turn your "To Do's" into "Done" by scheduling them into your day planner or calendar.  If you send your invitations 1/2 hour before the party, all the rest of your work may be in vain!

• Get some help creating your lists if you need it.  You can hire an organizing coach like me, or find dozens of pre-developed lists online at List Plan-It.  They have a subscription service that provides lists for just about any occasion.  You can download their forms and add your own details.  I'm not affiliated with them, but I think they're a great idea.  They save a lot of time thinking of the categories you need.

• Finally, when your event or activity is over, whether you worked from a list or not, create the list you wish you had had at the beginning (or update the list you used to include the parts you forgot, did too late, etc.).  Put this in your list file so that next time you will have the perfect, custom list to make your event go perfectly.