These tips are based on my personal experience.

1. Don't announce your forum until it is 100% ready, incomplete categories, 404 pages and spelling mistakes make the first impression very bad.

2. Don't announce your forum on other forums wherein you have -50 posts at least, you should have good no. of posts so that people can trust you and should give your forum a look, otherwise they will treat you as spammer.

3. You shouldn't wait for others to come and put content in there, in the initial stage of your forum you will have to put the content yourself.

4. Don't make posts like "How old are you", "How many forums do you use"....etc, forums are already filled with such questions, you need to post informative content because if people don't join or post in your forum they should come back to read a new and informative post.

5. Be patient. Forums are really not easy to make famous but it is also not impossible, if you put quality content you should see the results in a few months.

6. Do not post your content on other forums, this way when users come to your forum they will find a new information which they have not read on other forums. Some of them will copy-paste it on other forum and few of them will give you a link back too.

7. Do not try to popular your forum overnight, it doesn't work like that. You need to wait and keep the forum grow on its own.

Hope these tips will be useful for you.

If you want to add any tip(s), you are welcome.