You do not say which version of phpBB you are using as the recommendations are different for 3.0 and 3.1
yaooke wrote:How often do I have to make back-ups?
That depends on how busy your board is - I backup every hour, some backup once a day, others once a month and some never back up.
yaooke wrote:Do I have to do other things then making back ups in case something goes wrong?
If you have not changed any core files then the only other things that need to be backed up are the files, images and store folders as everything else can be reinstated from downloads. If you have changed core files then you will also need to back those up as well (or as a minimum keep a note as to what you have changed)