This is probably one of the most important documents you'll learn to use. The best program to use for timelines is Excel (in my opinion). Other people use Microsoft Project for their overall project plan, but I'm not a huge fan of Project. Excel is a very important program to learn to use. It is capable of doing many, many things. Also, most people have Excel on their computers. The same is not true for Project. When creating a timeline, I start out by looking at the various functional areas and what the respective deliverables are. Work with your contacts in those functional areas to establish realistic deliverable dates.
For the format, moving left to right on the page, I usually have the following columns:
Days Out - meaning how many days before the event is the task due
Date Due - the date that this equals
Task - what needs to be done, in detail
Responsibility - either the person's name or the department's name
Notes - any special information
Sometimes I will add a Date Completed column. I will do this in a situation where it's a new event that will be a repeat event, and I don't know how long it will take to complete a lot of the tasks.
I also put an auto filter on the entire document to allow sorting to be much easier, especially for very detailed and long timelines.
If you're working on repeat events, you can set up a template timeline. Put in the number of days out that the an action needs to take place (e.g., signage ordered 30 days before the event). With Excel you can create a formula that allows you to simply enter the date of the event in a cell (I put this cell at the top of my timeline), and the due dates will fill in the second column based on the number of days out previously entered in the first column.
Timelines keep everyone on task and keep the project moving forward on a common schedule.