A MUD needs players! There's no way around it. Logging in to a ghost town MUD isn't any fun. You'll quickly give up and move on without support, companionship and most importantly PK victims. (Note that you cannot be PKed unless you choose to be a Pkiller.)
The more players that Dune has the better it is for everyone. The community will be richer, the wizards will have more motivation to code, the playerkillers will have more people to playerkill.
Ultimately though, we all must admit that playing a MUD is quickly becoming a fringe hobby. The only way to keep our game alive is for everyone to chip in and spread the word. If you really enjoy Dune let the world know!
Promoting Dune can be as quick and painless or as involved and dedicated as you want. At the low end of things, why not just tell a friend? There is no shortage of players on Dune who were welcomed into the community by a friend.
Alternatively Dune is listed on several “Top MUD Sites”. The higher in the rankings Dune is on these sites the more visitors we're likely to attract. You can easily vote for Dune in two clicks. It's so easy, why not do it?
If you're feeling especially productive, Dune could always use a review! Write your thoughts about Dune, what you love about it, what keeps you logging in after all of these years. Dune has a Facebook Group, and there are plenty of other places to post your positive thoughts!
If you're promoting Dune you need to remember that you are acting as a diplomat for our community. Try to be respectful and positive. If you perceive flaws with the game nothing positive will come from discussing/posting these issues off-site. Staff won't see it and change won't come. Try to keep external reviews/commentary on Dune positive. The more certain you are about Dune the more players we'll attract. The more players we attract the more voices to be heard, the more potential coders, and the more motivation to get work done!