There is not just one answer to that and there is no simple solution. However, there are some things that work for me that I would be happy to share with you to try to help you get your ActiveRain posts found on Google.
First, are you a rainmaker? And are you making your posts public? Google cannot index members only posts.
Secondly? Are you writing what you think are clever headlines instead of Keyword rich think like a consumer headlines? Recently I saw a question where a member asked if others were having problems with their posts here ranking. I did a quick look through of their last 60 posts looking at the headline and first paragraph and I had zero idea where they worked. Nada. That's not good. When you write a headline you need to think "what will my potential clients be searching for on Google" and work those words into your headlines. Some of my examples would be thinks I use that really have gotten both found and made the phone ring are:
Lake Sinclair homes with pools
Lake Sinclair homes with garages
4 Bedroom homes on Lake Sinclair
Forest Lake Village, great neighborhood on Lake Sinclair
Crooked Creek area on Lake Sinclair
Those have been words that my Google analytics show are popular search terms and looking at my site analytics is very helpful in writing headlines. If you have a website you should check out search terms and know what people who do find are typing and then expand on that by using those terms and similar terms in headlines. As winter grows close I plan on doing a post on Lake Sinclair homes with fireplaces. People love a fire and winter and I'm going to take advantage of that opportunity.
Hopefully you find this helpful and can get your posts ranking and your phone ringing too.