How to merge between branch and trunk multiple times with tags - quick questions

Hi All

We're new to CVS and we need to merge trunk changes to a branch from time to time.
We are not sure how the -j option is used for the 1st merge from trunk to branch.

We are also unsure how the multiple -j options are used for subsequent merges from trunk to the same branch. 

What's the syntax to merge back from a long lived branch to the trunk?

Are there examples on how we should tag before and after a merge ?


Thank you 
Sincerely