If some of your sites are related topic wise, (for example, you have 1 site about cuban cigars, 1 about hand-made cigar boxes and possibly another about quality lighters) - you could use the same code for your opt-in form for all 3 sites and send your lists the same newsletter and just keep your content related and interesting. This saves you some time and work
How often you should mail?
That is your call, but personally I mail my subscribers every 4 or 5 days when they are "new" so I can give them enough interesting stuff so they want to hang around on my lists. Also, due to different time zones and so on, some people may be "unlucky" enough to be starting work or something else when your mail arrives every Tuesday, so the delivery day is good to "juggle" a little - but bear in mind to let your subscribers know when you will be mailing them again.
Mind you - if you keep your subscribers interested enough as other members have touched on - they will be waiting for your newsletters. Go getém
