Finding your graticule
There are a few ways to find your local graticule. You need to know it in order to find where to go on your expedition, and you should probably bookmark the wiki page for your home graticule because you'll use it to communicate with local geohashers.
If you know your home GPS coordinates
Start by figuring out which graticule you are in. If you already know your home latitude and longitude coordinates, then look at the whole degree portion only. If the latitude is north consider it positive. If the latitude is south, put a minus sign in front of it. Likewise for the longitude. An east longitude is positive and degrees west are negative. For example, I am writing this sitting at N58 48.157 W122 41.335. My current graticule is therefore 58,-122. Note the comma, no space. You can type that right into the search box at left and hit Go. That should redirect you to a page showing the name of that graticule. If it doesn't work, try one of the following methods.
By place name
If you live in or near the largest city around, chances are your graticule is named after that city, or at least named on the graticule page. Try typing the name of the city into the search box to the left. Click Search (not Go). Look for a page in the results list that describes the one degree square in which you live. It may be that you are in the next graticule over and can click the links above the map to get there.
The graticule page typically has a map and description of the graticule, a list of local geohashers, and links to previous expeditions. There should also be a today's location link on that page. Click it and it will take you to the peeron map, with a red teardrop pinpointing the day's location.
If you can't find the page, or the today's location link go to the next section.
Using the peeron map
Go to the Coordinate Calculator (which everyone tends to call peeron after the server where it is hosted), zoom out, and scroll around the world as necessary to find your home. Click on where you are so that a red rectangle appears around it. If your graticule has been named, the name will appear at the bottom, in a row beginning with the words Wiki pages: Day / Meetup /. The name is a link that will take you to the graticule page. You can click a button to set your graticule as the default for next time you use this application.
If there is no name (you may need to wait a moment for it to appear), or if when you click on the name it takes you to an edit box instead of a page, then no one has yet created a page for your graticule. You have the honour of being the first geohasher there.
Note the coordinates, in which ever style your GPSr uses, plan a safe route, bring anything you'll need, and go!
We all hope to see you at our coordinates someday, and look forward to reading your report when you get back.
Also see the links in on the Help:Contents page.