What is the recommended workflow and repository layout for single developers?

There are certainly a few ways to answer this. The ideal workflow that we have in mind has not quite been finished yet:
http://bazaar-vcs.org/NestedTreeSupport
http://bazaar-vcs.org/NestedTreeProgress

The idea with http://bazaar-vcs.org/NestedTrees is that you can have a project made up of subprojects. We have the internal infrastructure to support it, but we don't have all of the commands (push/pull/branch/etc need to be revised to handle when the branch is an aggregate branch).

In general, Bazaar (and pretty much all of the distributed VCSes) version the entire tree as a single entity. You might consider it a "project". So if you have libraries, etc, that you want to share between projects, then they would be considered a separate project.

If you work that out after the fact, we have written the "bzr split" command, which takes an existing tree, and 'splits' out a subdirectory into its own versioned branch.

I would also recommend having an overall Shared Repository (http://bazaar-vcs.org/SharedRepository) at the top, so that any branches you do create end up sharing storage.

Also, there is a slight terminology mismatch between DVCS. Bazaar considers a repository as only the location where data is stored, other systems mix that term with where your working files are, and where the branch pointers are. In Bazaar, the Repository doesn't have to be in the same location as the Branch or Working Tree, which is how you can have multiple Branches sharing the same Repository.

So your question of "should I have a repo in every directory..." is actually (in Bazaar terms) "should I have a separate Branch in every directory...".

> If you work that out after the fact, we have written the "bzr split" command, which takes an existing tree, and 'splits' out a subdirectory into its own versioned branch.

Where can I find this split command?

I cuurently have the following format:

$bzr info development
Standalone tree (format: dirstate)
Location:
  branch root: development

How do I convert this into a shared repository?

To move a branch into a shared directory, make a repository directory and branch into it, eg

  bzr init-repo ~/repo
  bzr branch ~/standalonebranch ~/repo/branch

then the revision data will be stored in ~/repo/.bzr, and used by all branches under that directory.

The 'split' command is built in to bzr -- see 'bzr help split'.

I have a question about it too. I want to familiarise with code structure for programming. I start with very little projects to learn. There's a point that I don't understand. Suppose that I have a little shell program: 2 or 3 .sh files, a default .config file, an icon... How can I structure all this for development and testing? For example, programs are often installed in /usr/bin, user config files in ~/.program, icon in /usr/share/pixmaps... How can I put all these files of my program in the same place to develop it, test it and then manage its versions with bzr?

Thanks.