The heart and soul of Ra is, of course, the auctions. Make the wooden Ra totem your friend and it will see you to victory.
Calling an auction by invoking Ra is incredibly powerful because it allows the auctioneer to bid last; the batch of tiles can be bought as cheaply as possible or let go if the price is too high. Calling an auction is compelling because there can be no bluffing: even if an opponent would like to "stick you" with the batch and decline to bid, those tiles are lost to the opponent forever. The #1 mistake in Ra is a failure to call auctions often enough. The mistake persists because it is not as blatant as a misprioritization of tiles (too many pairs of monuments!) nor as memorable as pressing your luck with the Ra track--it simply results in your opponents getting more and better tiles than they should. I have chosen the theme of this article to highlight the importance of calling auctions: Calling should be your default assumption, and I will examine here the various reasons why you might not want to.
For strategy and guidance about the value of suns and tiles, check my earlier article here.
First, the easy ones.
The batch is worth too little for anyone to bid on it.
This is the most obvious one and needs no further explanation.
You plan to buy the batch with the largest sun remaining, and want to add value to it.
This is another obvious one. If you are definitely going to drop the biggest sun remaining, no reason not to increase your prize. You still might want to call if a particular disaster (Flood, Unrest) would be particularly devastating or if the Ra track has only one space left.
Now for the interesting ones.
The value of the batch is intermediate, and you would like to purchase it.
Example: Your suns are 2 and 11. The batch is worth about 7 points currently and is particularly attractive to you because it provides your 5th and 6th unique monuments. The 2 won't be enough to buy the batch, but you hope for more from your 11. So you draw. Note that if the batch were not particularly attractive--for instance, if it contained a flood while you already have one, or a duplicate civ--you would call.
Drawing a tile is likely to bring the batch into the "good value" range for one of your suns.
Related to the last point. If the batch currently does not look like a good value for any of your suns--but it might be, if an average tile were added--you may choose to pull. If the batch is currently better for you than for the other players, this becomes a better option; conversely, if you can force another player to take a batch you don't want sooner, calling is advantageous. If you pull, some other player will probably call an auction before you, but you will either win your tiles or force out a bigger sun.
You want a specific opponent to win the batch with a big sun.
Example: Because of the nuances of monuments, civs, and so on, the current batch is worth 8 points to Opponent A and 15 to Opponent B. Opponent A has the highest sun; B has another high sun; I have only a low sun and no particular chance of winning this batch. Furthermore, Opponent A is not doing very well but Opponent B is a major threat. If I call an auction now, Opponent A will probably pass, hoping for more from his supreme sun, and give this auction to Opponent B. Rather than letting this happen, I will draw, hoping to increase the value enough that Opponent A will eventually buy it and deny Opponent B this windfall.
You want to ensure a batch is not bought cheaply by a particular opponent.
Example: The batch contains nothing but a pharaoh and a monument--unremarkable except that it's worth 10 points to Opponent A, who is 1 pharaoh short of tying for the lead and already has 2 of those monuments. If Opponent A would be able to buy this fantastic batch with a low sun, draw to increase the value of the batch to the other players and force the price up.
You cannot win the batch at a reasonable value, and you have a god tile with a good target.
Don't be in a rush to use up your god tiles; they're worth 2 points which can be significant. If you have a good chance at winning the a good batch anyway, you might as well call the auction and get your desired target as well as the 2 points. On the other hand, if you might not win the batch--or won't want to, as the price will be too high--there's no sense in not maximizing the value of the god. Go ahead and use it.
You and your left-hand opponent both hope to win big batches.
Example: I have the 12, the second-highest sun, and my left-hand opponent has the 13, the highest. I won't be able to win a really fantastic batch if it comes around unless I get rid of him, since he bids after me unless I call the auction. If we both draw to an already-decent batch and he wins it with his big sun, that leaves me to take the best of what comes afterwards.
You are hoping to pull a Ra or disaster tile.
This is a desperation move, but sometimes the last few Ra tiles come in a hurry! If the Ra track is one space from full and you have little hope of gaining anything from your remaining suns, it can be valuable to draw, even to an already large batch, in the hopes of pulling Ra (denying the value of those tiles to the other players) or a disaster (reducing it).
And just to drill it in, some common mistakes; times when you definitely should call an auction.
The batch is already out of your price range.
Call the auction and get one of those powerful suns out of the way, giving the opponents as little as possible.
Pulling a tile won't make the batch a good enough value.
Example: Out of ten suns remaining, you have 1 and 13--the worst and the best. The value of the batch is currently in between, but drawing won't bring it up to be a good value for your high sun. In this case, just call. All the intermediate suns are the same to you, so get rid of one of them, again, giving away as little as possible.
The batch is worthless to you, but valuable to others.
Remember: Sticking you with it means that your opponents miss out too. Someone is going to buy it, so have it auctioned off and hope for further tiles to come that are valuable to you, not so much to everyone else.
Credit: Karl Rainer