Tim, I would guess you are referring to the Trade Announcements / Offers Section (
Trade announcements and special offers - RIBnet Forums) rather than the directory (
RIBnet directory).
I think there are a number of reasons why it is quite nice to "keep it separate" rather than encouraging you simply to post your deals on the main forums. Not least of which is that random other people can't reply (publically) to your posts and get into a discussion/argument or other trade members saying "we will match that" etc.
From a user perspective I don't really notice which forum people have posted in and mostly 'browse' using the 'new posts' link at the top, so see everything. I know this is a popular approach - but I don't know how many will miss or avoid threads which are in that section. I suspect being 'blatant' about it being a deal is better than putting it in the main forums and p*s*i*g people off with a constant sales stream.
As with all forum threads a carefully worded title may be key to getting people to read on. E.g. I notice your last post in that area only got very few views (and it was a couple of weeks ago) whereas some of your previous posts have racked up "average" views for that section. The difference might be the specificity of the title. However if you look at the 'popular' threads in terms of views they seem to have the 'discount' 'deal' or 'special offer' clear in the title. You need to do more that run a course - you need to present it as a "bargain". Of course views may not = bookings.
Posting ads here even if they don't get many bookings directly can still help by raising your profile in Google. There are some key things to do though which will help Google know that Tim Griffin training is THE place to go for training... ...a quick look at your last couple of announcements suggest you are not making the most of this.
In terms of other advertising I guess there are a couple of things you can do:
(1) Be in everyones' face by changing your signature to promote your latest offering.
(2) Pay for google adwords to get on the banner ads.
However, Willk is probably right, my first port of call for some expertise or equipment would probably be someone who ads to the community (not suggesting you dont) rather than someone who only logs in to post ads, or who always seems to be promoting themselves. Either way though there are a lot of training schools around and you need to be "known" to get business.