Recommending products and services is fine, selling or promoting stuff except relevant items in the Members Ads, is not.
Post in the relevant forum. You can move any thread you started if it's in the wrong place (see how here). An administrator might move it (but would prefer not to have to!).
If the thread drifts off topic, start a new thread in the correct forum and link to it.
In the unlikely event of seeing unkind or unhelpful posts, speak nicely to the offender, they probably didn't realise how they came across online - it's easy to forget how many cues are lost when it's just text. Emoticons can help (apparently).
For really bad stuff Report Content As Inappropriate with the flag icon on far right of each post's subject line. Offenders will be made to walk the plank or be banned by the forum administrators. Anyone banned can appeal to the DCA management committee whose decision is final. That's the boring - but important - stuff over.
Don't stay up too late…
"Selkie", a Drake rowing boat by Clint Chase
"Scratch", a Walkabout dinghy by John Welsford
Mainly sailing and rowing on the Firth of Forth forthsailoar.osbert.org