How about
indirect advertising (within forums, specifically)?
I think there are many ways one can promote themselves/their animals without directly/consciously doing so. Posting images (within a discussion forum) of what you've produced allows you to talk about your pride and joy, and it gives the rest of us something to drool over. I wouldn't be surprised, though, if some of those animals which were intended to eventually end up in the classifieds, never make it that far. I'm pretty sure a few inquires are occasionally sent the OP's way, based solely off that thread. On several occasions I've taken note of who to contact once I'm in the market for a project that they're working with...because of what they've posted on a their "check out my X animal" threads (i.e. April, when I'm ready to tackle Boas again, I'm coming to you for Sharp Albinos

).
Offering husbandry info. There are always reoccurring names who give advice when its solicited (sometimes even when its not). This is something that I also take note of. When one has a wealth of knowledge which proves itself (over and over again) to be effective, it often stems from personal experience. Those are people who's animals I'd probably want in my collection...for many reasons. If they're
that willing to share advice and offer help, then I'm leaning towards them going above and beyond while taking care of me as a customer (if any issues arise, they'll be there). Also, they are more likely (IMO) to have a collection of healthy animals (based off of a solid foundation of proper care).
I've also seen members utilize the
testing area forum for indirect advertising (whether thats their intent or not, that's exactly what they're doing). That forum does not get used very often, hence, whatever is posted there will most likely end up visible for a day or two to come. Out of curiosity, I check out new threads posted there (I'm sure I'm not alone). Sometimes you'll find "test ad's" which are formatted for the classifieds (with or without prices is irrelevant). That's exactly what that forum is for...to "test" different posting options/features on this site. Thing is...I sometimes see very senior/experienced members posting such things. They know the routine, lol...I don't see what exactly it is that they are "testing." What they're doing is promoting themselves within a sparsely used area of the site. Ultimately you have an ad up (which wont need to be "bumped") staring everyone who enters FC, dead in the face. Again, even if advertising is not their intent behind posting a "test ad" thread...I think they are inherently doing so.
Having said all that...there needs to be a combination of many things for me to "trust" someone. However, since we're only talking about getting one's name out there, I think that indirect advertising within a forum is very effective but sometimes overlooked.