I\'ve been reading up on branching/merging with Subversion 1.5 using the excellent and free Version Control with Subversion book. I think that I understand how to use the S
You should use "merge a range of revision".
To merge changes from the trunk to a branch, inside the branch working copy choose "merge range of revisions" and enter the trunk URL and the start and end revisions to merge.
The same in the opposite way to merge a branch in the trunk.
About the --reintegrate flag, check the manual here: http://tortoisesvn.net/docs/release/TortoiseSVN_en/tsvn-dug-merge.html#tsvn-dug-merge-reintegrate