This is my 1500th (Including all crypto sites, pbns and other money making sites) post and thus thought to giveaway a method which is revolving in mind for some days.
Method:
Pick a popular forum and find what keywords it is ranking for alongwith corresponding urls. This can be done with the help of paid tools like ahref or semrush. You need not buy these tools, you can simple get one time data for a url by ordering a gig on Fiverr.
Now pick keywords that can be put to use. For instance, suppose you have a small hosting company. Find keywords related to hosting like best host, reliable hosting 2018 and so that the forum is ranking for at higher positions on Google. Go to corresponding url and leave a reply there with link to own company. Make a quality post there so that you pass moderation.
This can be done in all niche like crytpo, health and finance. Apply twists for better results. If you have any doubt, post below. All the best.
Edit: Don't this on HERE. You will be caught and punished.