I agree with the accepted answer, but in our case we need to be concerned about service offers more than that question's focus on product recommendations.
A few points not in the accepted answer that I think are important:
It goes without saying that an answer needs to be a valuable contribution in the context of the question asked in any case.
Don't post about your own service or product without disclosures as that is essentially misrepresenting something - most readers will assume that your opinion is unbiased, and it's not. Saying 'our' or 'my' service is good enough disclosure. Alternatively, adding that you are the CEO, Owner, or an employee of a shop in a post mentioning its solution or service is appropriate.
Posters should beware that posts that are too 'sales-y' will get voted down or marked as spam. I like an approach that evaluates each post on the balance between useful content helping the questioner and unnecessary or extraneous content that is spammy. Moderators end up responding to these flags and making their judgements.
Tip: When answers mentioning one's own product or service also point out good alternatives they seem much less spammy.