Here on Wikia you've got many options of messaging users. In this blog post you can find all help with messaging users and which options there are.
On the userpages of users you can go to their message wall or talk page to leave a message to them. It's an nice place where you can message to that person you want to question/talk.
The message wall is one of the options you can enable at Special:WikiFeatures. If not enabled there are standard talk pages. On the message wall you can leave messages to one person, after messaging this user get a notification, so people see when they get a message and can respond directly if they see the notification. An advantage of the message wall is every thread has his own place.
The talk page works similar with the message wall, but it has another notification system. An advantage of the talk page is people an be more creative.
If you want to let the wiki know something of get some attention, a blog post is a good idea to share your ideas and things. You can start a blog on your userpage. Normally this feature is standard on a wiki, but it's possible the blogs aren't enabled.
If you want to ask something on the forums or want to share something with the community on the wiki, the forum is a good idea. If you want to enable the new forums like here on Community Central you can enable it on the page Special:WikiFeatures.
The community message is shown on the Recent Wiki Activity page on the rightside on your wiki. You can add some information about the wiki, get attention for something or show the current projects on your wiki. Also people who visit your wiki get a notification the community message is edited automatically.
Another option is adding the message or what you want to tell on the home page of your wiki. Many people visit it, so also many people will see your message. A disadvantage of messaging via the home page is that it's hard for users to message back.
It's also possible to message people in the chat, but of course people are not always online, so you need some luck if you want to talk with people directly. Also if you want to use this feature you have to enable it on the page Special:WikiFeatures.
On pages on wikis you can comment, but normally you want to talk then about that page or the topic on the page. Also you have to enable this feature first on Special:WikiFeatures.
If you want to know what people love/like/dislike more you can use polls or top 10 lists. But also this features must enabled first via Special:WikiFeatures.
If you have questions about messaging or want help with something please go to my message wall to ask me about it. You can also ask an admin on this wiki, go to the forum or ask in the chat.