Configuring the wiki
As a new user your wiki account has default settings. Here are a few suggested settings and other tweaks to improve your experience here. Unless otherwise described these are in my preferences near the top right of the wiki window.
Know who is talking to you
Your talk page is where users leave messages for you. This is a common form of interuser communication on the wiki. In the User profile tab, give an e-mail address (it will not be displayed on the wiki) and then people can send e-mail directly to you. If you also check the box for E-mail me when my user talk page is changed, that will happen too.
Know what people are saying about things that interest you
Almost every page on the wiki also has a talk page, and people leave comments on them, too. If you upload a photo, write an expedition report or participate in a discussion, people will comment on your contribution to the wiki and you probably want to know what they are saying. The wiki can remember and tell you about changed pages.
In order for this to happen, you need to watch the pages you want to know about. You can do this for individual pages, selecting the Watch tab on any page, plus you can do it automatically for pages you create or edit, by checking the appropriate boxes in the Watchlist tab. At minimum you should watch pages you create (Add pages I create to my watchlist). Then when you log on you can click My watchlist at the top right of the wiki page and see what has changed.
It's recommended that you watch the pages of any graticules you regularly geohash in, so you don't miss expeditions or new users joining the wiki. If someone proposes or makes a change to a page you are watching and you disagree with the change, you can discuss the issue on the talk page. Likewise, if you make a significant change to a page, you should watch it, in order to respond to others' comments and concerns.
If you don't want to have to log on to know when someone has changed something, check E-mail me when a page I'm watching is changed in your User profile and that will be done.
The default search space is quite small and misses a lot of what you may be looking for. For much better results, under the Search tab check every single box except for MediaWiki and MediaWiki talk. Now you'll be able to find pages on the wiki when you use the Search button.
Get the news
The wiki is in a constant state of change. You can see a list of recent expedition plans and reports in Current events in the left nav bar. A banner at the top of that page (and also on the Main Page) lists recent major changes and proposed changes that are being discussed. The source of that banner is the New on the wiki template, which is also a page you can watch.
If you want to see every little change people are making to the wiki, the Recent changes link in the same left nav bar shows all recent edits (except bots, unless you specify those too), but you're probably not that obsessive.