Our friends in the movie industry are using Facebook Pages to promote their upcoming movies. But their Facebook pages are not exactly about the particular movie, something like a general page for showbusiness. I think it is effective when it comes to promotion because so many pages that I see are like that. I almost forgot, a more potent promotion is using a Facebook Page of a celebrity particularly the star of the movie that is being promoted. Especially if the celebrity has thousands of avid followers, it is really effective to use his page for purposes of promotion.
For a personal website or forum, I guess you have to use a page that is relevant to your forum.
I use dozens of FB groups to promote my blog posts. It works great. I use a social media management tool, therefore almost everything is automatic. I only have to create the posts and violà. I get 100s of clicks for 10 minutes of work.
That's right. I see that many guys in Travel field at Instagram usually have many tags on each their post. This will increases the chance other guys will see that post. IMO
I have used Facebook for increasing my organization reach among people. I have used facebook groups. i mainly used high quality and viral content and high images and video for this purpose.
I have found that posting in groups helps, but if you post the same link too often your link can get blocked. You can also get a 3-day ban if you post links in a comment too often. What they really want you to do is pay for their advertising.