If you haven't done so yet, join a game. Don't worry if the game has already started. To join a game, click the Join Game button near the top of the left sidebar. Follow the instructions in the main window.
Now you have joined the competition to see who will be the next Big Cheese!
Click the "Place Bids" button on the left sidebar to visit the auctions page. It may take a moment for the auctions to load. On the left of the main display area, you'll see a list of the items at auction during this Turn. For now, we are interested in auctions that you haven't placed any bids on. Those will say "No Bids" in the Status column. Click on an inviting item that says, "No Bids". If you can't find an auction with no bids (they will all probably say, "Passed"), that means that there are no more auctions left in the current turn. We'll have to look at the next turn. At the top of the auction list is a number box labeled, "Turn:". Click the up arrow to look at the auctions for the next turn. {Sometimes, the chat window (underneath the auction area) will hide this number box. If you can't find the box, you can shrink the chat window by dragging the divider bar down a bit. Look for three little white bars over the yellow line just above the chat window. Click-and-drag them downwards.}
To the right of the Auctions grid is the bidding grid. It will have a heading showing the item you are about to bid on, and an empty list of bids (since you haven't placed a bid yet). Go ahead and place a tiny bid, just to see how it works. Click the "New Bid" button, which is just underneath the bid list. A new bid has appeared! It's a $1 bid for a single item. That's not nearly enough, so go ahead and edit the "Amount Per Item" up to $10 (leave off the dollar sign, though). And since $10 is still pretty cheap, go ahead and bid on all of the items in the auction -- edit the "# To Buy" column for your bid to match the number in the "For Sale" column of the auctions grid. $10 still seems rather low, though, so let's add another bid at $20. Click the "New Bid" button again, and edit the amount up to $20. Leave the "# To Buy" at just 1.
After the bids look good, you need to click on the "Save Changes" button underneath the bidding grid.
That's how you place bids, but what does it mean?
Big Cheese auctions have sealed bids. This means that other players cannot see your bids, and you cannot see theirs. Also, since auctions are usually for more than one item, you can place multiple bids. You have effectively told the auctioneer that you willing to pay $20 for one of the items in the lot, and $10 EACH for whatever is left. If someone else bids $15 for 3 items, you would win the first item in the lot, they would win the next 3, and then you would get the rest. It's okay to bid on more items than the auctioneer is selling; any extra bids will be ignored.
Mind you, those prices are probably too low to actually win anything, but if you do win, what a bargain!
For some advice on winning auctions, but not paying too much, check out some Bidding Tips.
For more details on exactly how auctions work, visit Auctions.
Eventually, you'll win an auction, and need to find out about Using Items.
Ultimately, you'll want to know more about Winning.
All items are valuable, and worth buying. If you can get it cheap, buy anything.
However, some items have Specials that command premium prices.
In particular, as a starting player, look for Income and Special Liquid items. These will give you more cash, increasing your buying power. Be sure to read the section on Income, though, because it probably isn't worth buying too many of the same income item. Or, at least, it probably isn't worth paying a lot for them. The first one is well worth it, though!
If you have lots of warehouse space, consider Interest Special and Family Interest Special items. Those won't help your purchasing power, but the Big Cheese really respects a fiscally responsible mouse!
All of the various Specials are useful, but the ones mentioned above are particularly valuable, and often missed by first-time players.
After you get a feel for things, experiment with the other Specials.
Eventually, your Warehouse will fill up. You only have 8 slots in your warehouse to start with. If it gets full, you can't win any more auctions! Don't let that happen.
To free up space, you can give items to the Big Cheese. Indeed, that's how you will impress him! Give until it hurts.
Some items have Specials that you can choose to use. Using these items will clear them out of your Warehouse, and make some room for new purchases.
If you can get your paws on Warehouse Special items, you can make your own Warehouse permanently bigger!