It's tricky to use Reddit as a marketing channel but it has so much potential.
1. Be authentic. Redditors are kind of people that will call you out immediatlly if you try some bullshit marketing strategy there.
2. Give more than you take. Try to find 2-3 communities that are close to your product/service and engage in conversations be helpful and where it makes sense plug your product.
3. Post only high quality content. One strategy that worked for me was to post high quality content without any links, personal learnings/stories tend to the best. And then after few days edit the post and plug your link into it. It will have passed enough time for the moderators not to notice it, but it will still gain traction.
4. If you are trying to get fast results use
Howitzer.co . It's a reddit DM automation tool it lets you target people in certain subreddits that have used certain keywords.
That's pretty much it