GTD - Managing actions across project lists and next actions list

Some variation of this question comes up over and over again in GTD discussions -- how do I keep projects and actions properly linked? (I've been going GTD-ish things for several years now, and I still routinely fall off the wagon.)
Your intuition about not putting actions on the project list is right. The projects list is for projects, not for all the actions that make up the project. As you describe your system, it sounds like your projects list is really a list of projects and each one's action history. Limit your projects list to actual projects.
On your action lists, you may want to add an additional category in Outlook Tasks for each project, so you can display completed tasks by category, or you might prepend a project label on each action ("Taxes: Download TurboTax") so you can tie your actions together that way.
Maybe you'll get advice from an Outlook Tasks user who can give you more directly useful pointers.
flexiblefine
Houston, Texas, USA
DiSC: 1476

I think you're conflating several distinct categories of information into a single tool.  One of the things that it took me a while to "get" with GTD (and it has been about 6 years now) is that it all works better if you keep very hard and distinct edges between types of information and between your processing steps.
Your project list will work best if it is just that - a list of projects.  A short name and maybe a longer description of successful outcome, but nothing more.
Next Actions are simply "bookmarks" into the work needed to complete a project.  If you complete one and want to continue on that project, do it, no need to write every NA onto a list.  When you're done with working on that project for now, you might make note of what you should do next.  That would either go into your Inbox, or if you can immediately put it on a context list, go ahead.  You do not need to add it to the project.  If you don't do anything, you'll notice in your next Weekly Review that you have a project with no NA, and figure out what you need to add at that point.
You are doing a Weekly Review, right?  If you're not, you're missing a huge part of the power of GTD (and many other personal productivity systems).
Tagging your Next Actions by Project is one of those actions that is very common as people start to implement GTD, and eventually goes away as you integrate it into your life more fully.  You don't need to, your weekly review will keep you up to date on everything.
That said, I do sometimes find it useful. If you really want to do it, here's one way that will work in Outlook Tasks.  It also works in Remember The Milk, and any number of other list managers that allow unlimited tags or categories.  I'm going to say "tags" below, but read that as "categories" for Outlook purposes.
First, I suggest you move your project list into your list manager, e.g. Outlook.  Tag all your project entries as "^Project" or whatever you want to call that tag.  You can add a description of the successful outcome to the notes area of Outlook Task.  You can also tag each project with a unique tag for that project.  I start these tags with p-, e.g. p-2011Q2Reviews, p-201109Conference, p-CarTires, etc.
Then you can create Next Actions as needed.  Tag them with whatever you use to identify the context they land in, and also with the p-* tag that identifies the project the NA is related to.
Now you can create a view that orders or filters by category or tag as needed to create Project List or context based Next Action lists.  Or a list of actions by project.  You're limited only by how clever you can be in defining the view.
Hope this helps.
--
Dennis Sherman
6-1-2-7

Dennis - excellent description of the project list and next actions, I would just like to add one more part to this for the original poster - the project reference material - which may help with the next action issue.
Some projects may need some more information, including support info e.g. - key player names, locations etc , plus a plan or a more informal list of things that need to happen - nb this is NOT a list of next actions but just the project broken down into more manageable parts. If it is useful then you could track the project at this level.
The reason it is not a list of next actions is that the next action gets defined when you have stopped working on the project and is the next actionable thing to do in a specific context to move the project forward. You can not define it ahead of time as you do not know how far you will get when you stop working on the project and so will not know what needs to be done to move it forward the next time. The bigger steps are in the project reference material and could be defined ahead of time, it just depends on how much you need to plan.
hope this clarifies not confuses !
Roy

I have two years of GTD experience and have most of my directs starting on implementation.
When I started with GTD I used a spreadsheet for all parts except the calendar, date specific next actions. In this case, Dennis is indeed correct. You need VERY sharp edges on your different tools.
I am now using the Things app from Cultured Code. It is an Apple only product but it has really maximized my effectiveness. I can now list steps in projects which are automatically placed in the NA files as well.

Thank you everyone for this great advice.  I do believe is was conflating 2 parts of GTD, as Dennis said.  Having said that, I still think that it will be helpful for me to see which project my actions are associated with.  I'm going to eliminate actions from my projects list and try the "append project code to the start of actions" and see how that works.  If I find that it's overkill, I'll just drop it.  
The part that worries me about creating separate Categories for each Outlook project is that I've got 100+ plus projects, which would be a lot of categories and could get unwieldy pretty quickly.  
Did my FIRST weekly review last week.  So awesome.
-DB