Trade posts with other forum owners and build it up. Forums are tough to get going. They need a boost as do all websites. And then you have to continually market them. Forums like DP are not built over night.
Get a membership with other forums. Talk about your forum when possible. Place your forum in the signature. Submit your forum to forum directories.
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.
There are people or companies who you can hire to make the first 100 or so profiles on your forum and to start the first discussions. It's much easier to get new members if they notice that your forum is already popular. Nobody wants to be the first one there.
For increasing forum traffic, promote your forum with SEO. Post about your forum in other forums. Announce a contest for your forum for increasing members
I the beginning you need to be very active on your form to let people know the form is 'alive'.. The best way to get more traffic is to be good.. to be the best.. People want to know things fast on a form.. So the key is to give them the best information about the question. Try also to do something with social media
Link to your website in both your signature and profile areas. These features should not be too hard to find on the forum, and take only a few minutes to set up.