If you think this is fine and will work, just tip me the word and I will give you a list of sites I would like a link on, with my unique feature that no other soccer forum has, and we will count the links that appear in my analytics after say two weeks.

I'll bet it will be slightly less than 1, and you will be banned from most if not all of the site for spamming.
You say "after becoming established" you do realise that could be 1000 posts on some sites before you are no longer considered a noob !
On some sites you even need 100 posts to have a signature, and the links are no-follow, which are about as good for SEO as chocolate is for making a fireguard.

Firstly, you can do that if you desire, goodluck finding someone else to do that for you... and secondly, what I posted about was sharing an article on your forum, not promoting or shamelessly saying what your site offers that another doesn't.

I think you are missing the point and dare I say a little naive, leaving any kind of link on some sites is impossible, if the whole post isn't deleted, the link as a minimum will be. I would hazard a guess from polite enquiries I have made that over 90% of soccer forums wont even consider an affiliate link, one wanted ?50 per month for an advert.

It's tough today.

Things have changed.

You're competing with social sites now, and back then there was only Myspace...

It depends on the niche though, and how you can stand out or reinvent things.

With that said there's no answer, other than working hard and having a bit of hope.

And... Staying with it. Far too many forum owners just give up.

It really depends on the site admin's individual views on that. They might allow sharing linking in specific forum, in your signature, as your home page or only when it's contextual. My site, and owners of it before, have always allowed link sharing as long as it wasn't in the sense that they were trying to steal members. Not everyone is is thinking (or values) SEO.

The key thing a site needs is regular, unique content. The link sharing and other tools can help get the ball rolling, but ultimately, content is what will get the users to come back.

I started a site and did nothing apart from make it look good for what it was for.
The site's content is the same as a few other sites with a kind of small community
In one year there's been 10 posts by real members, everything else came from me.

I started another site where no one or no other Forum content was the same as mine, but there was a call for such a site.
Google and the search engines did their job and a year later it's a nice busy site.

your strategy must need changes...big changes

netticasinot

Content is King. Fresh content keeps people coming back time after time. That's easy to say but a little harder to do. That's where you have to devote time to keep it up.
KISS Keep it simple stupid. Easy to navigate menus make it simple for even non forum savvy users to find what they want to look at or do.
Moderating. This is a slippery slope to step out on. You have to show people you mean business but in a way that doesn't drive them away. A hand on the shoulder and a whisper in the ear, works better than belittling a wayward member in the open. Take it to the PM's.
Be flexible. Listen to your members. In all the suggestions, nagging, and whining, there comes that one really great idea that didn't occur to you.
Running a forum is hard work. But if you really enjoy the subject it's built around then it's a labour of love. Whether it makes it or goes down the drain, is up to you. Keep hammering at it.