In my point of view.
You want to sell thing, you need to promote stuff.
1. Don't spam the timeline either in Fb or twitter. Its annoying especially person like me who view the social network by phone. All you will get it either Hide or Unfriend.. by me. Sorry.
2. Tagging is ok (for me it does help in spread the news) but please keep it once. You don't have to tag every single item with that same particular person. Again, its annoying. Rule #1 will reapply here.
3. Make your own Facebook page and promote your stuff there. Beg your friends to like and share your page. Makes giveaway. It helps in increase the number of page-Likers.
4. And do not double post; you don't have to promote on ur Fb page then in your personal Fb. Its confusing and ya, annoying. You can do that for the first few time at the beginning when you start your page but once the follower reach 100 stop do that. Time is precious. Focus on the stuff to sell rather than just promotional. Customers will come naturally. Believe me.
5. Sell good stuff with good value. If you're Muslim always make self-reflection. We manage to sell because Allah swt help us and the rezk is barakah. Mebe when we fail to sell is time to look back. We might have push it hard till we neglect our right to serve Allah. Eg: We push to sell from one house to another, sitting hours in front of the computer searching for buyers (and pray at late hour- hujung waktu) or like me, sewing till late night and miss Fajr (Astaghfirullah) or mebe to busy we even forget when the last time we read the Quran. Its time to look back. Yang baik is from Allah swt and obviosly yang buruk comes from us . Wallahualam.