In the first place you will have to think about what it is that needs to be done in order to achieve the project goal.
I find that the best technique for this is to get some coloured post it notes blue for headings and red for things that are beyond my control yet I depend on (dependencies to the experts) and finally a big pile of yellows (the most common type) for all the things that make up the bulk of the work. The Blues and Lighter Blues head up columns of yellows for the tasks that make them up, with the reds (or pinks for internal to organisation but outside of my control) then go to one side. This may seem pedantic, but as you will see below it is important.
Then I will talk to each of my team individually and brainstorm what needs to be done to reach each of the blue goals and if we have missed out on any of the blue goals. Then we brainstorm all the items that might cause us to stop reaching them. Over the course of about a week (YES A WEEK NOT ½ HOUR!!!) We get a pretty clear idea of what needs to be done. OK much of that week is spent in getting to know the business of the project's sponsor and starting all the pre project work it is not all planning.... but it is a good way of getting a visual depiction of what the project is. Since many people think it is fairly barmy, I call it the Batty Technique I know my former colleagues at Primavera would roll in their graves if they were not happily alive developing excellent planning and control software, but fear not, the next step is to start getting it into a formal planning tool.
So now gentle web cruiser, you have a lot of boiled slug on the wall (that is what the glue for post it's is allegedly made from) now we need to get technical. From the layout of the Blues and Yellows you will have a fairly clear idea of the key headings and the items (and sub headings maybe) that make up the project are. This gives us a breakdown of the work or put it another way a Work Breakdown Structure (WBS a term you may have heard of) Each of the top level blues gets a major number, the lesser blues a "dot" number and when there are no more blues then the yellows have number of the blue post it at the top of their part of the column.(Fats Domino?) Sound Complex? Look here....
The first column is series one so the first real activity has a work breakdown ID of 1.1 R3.1 is a Risk (or dependency) on series 3.1.
Ok Lost yet? Never mind, think of the dark blue as heading one, lighter blue as a sub heading, and then the yellow as paragraphs of text. If this were a technical document then this is how they would be numbered.
Now the easy part.
Work out how much resource is needed for each task, (forming a resource profile) and how the activities/ headings depend on each other. This you then feed into a suitable scheduler and archive your post it's. The headings become your work breakdown structure and your dependencies/ risks your external links. I am not going to detail how to do this on each package but suggest that if you are unsure then contact a suitable reputable trainer (See resources page and Project Manger Today).