How the Bidding Works
Bidding runs two rounds. Both start with the player to the dealer's left and move clockwise, one turn each per round.
Round one offers a single suit: whatever the up-card is. Order it up and that suit is trump, and the dealer takes the card into hand and throws one away. For the dealer, ordering up is just picking the card up. If all four pass, the dealer turns the card face down and that suit is barred for the hand.
The second round opens the other three suits. Name one and it is trump, with nobody picking up a card, so the hand is played as dealt. If everyone passes again the deal moves left and the cards go out fresh, unless the table is playing stick the dealer, where the dealer has to name something.
Whoever calls, in either round, commits their team to three tricks and can declare at the same time that they are going alone.
The Three-Trick Benchmark
One question decides every call: can this hand take three tricks with the suit I am naming? Three or four tricks scores a point. All five is a march and scores two. Fewer than three and you are euchred, which hands the other team two.
So you are risking two points to gain one. A call you get right half the time loses your team points over an evening; aim to be right closer to two times in three.
Your partner will contribute, but plan on less than you would like. The old rule is to count on partner for one trick, which means your own hand needs two. In Cutthroat there is no partner and the same hand needs all three by itself, so callers there should be correspondingly tighter.
Hands That Are Worth Calling
The strongest holds both bowers: the right bower (the Jack of trump) and the left bower (the other Jack of the same color). They are the top two trump and take two tricks however the deck fell. That is a call from any seat.
Next is the right bower with two other trump and an off-suit ace. The bower is certain, one of your small trump usually wins once the bowers and the ace of trump are gone, and the ace wins unless somebody is out of that suit and trumps it. Two solid tricks and a likely third: a call, but not three guaranteed.
Two trump plus two off-suit aces depends entirely on which trump. With a bower among them, call. Two low trump is closer to a pass, because low trump wins nothing on its own and both aces can be trumped.
A hand with no trump at all is a pass however good it looks. Two aces and a king off-suit might take one trick between them, because off-suit cards lose value the moment trump is named. Ordering up on that is the most common way to buy a euchre.
What the Up-Card Tells You
It is the only card everyone sees during the bidding, and it affects two decisions: yours and the dealer's.
As dealer, a Jack of trump turned up is a large upgrade. You pick it up, discard your worst card, and hold at least one bower. An ace is nearly as good. A 9 is rarely worth it unless the hand is already strong in the suit.
Ordering up also hands the dealer a card, and when the dealer is an opponent that is a real cost. Never order up a card you would not want the other team holding. A 9 does little for a marginal hand and still gives an opposing dealer a free trump.
Seat Position
First seat (left of the dealer) bids before anyone has revealed anything by passing, so first-seat calls should be solid. You commit first, and both opponents then defend knowing the suit and knowing you were willing to bid it.
Third seat (the dealer's right, partnering first seat) is the most flexible, because two players have already passed and the second pass is the informative one. Second seat is the dealer's partner, so ordering up would have handed the up-card to their own side; turning down a call that cheap says they have nothing in the suit. What third seat does not escape is the cost of ordering up, since the dealer is still an opponent. Better information, not a free call.
The dealer's seat is special because of the swap. You trade your worst card for the up-card, so the hand stays at five but gains a guaranteed trump and loses your weakest. Order up almost anything that becomes three-trick capable once you have made that trade.
Second-Round Bidding
Passing in round one tells the table your hand did not want the up-card suit. If your real strength is in the same color, that pass cost you nothing.
Calling the same color as the rejected up-card is going next, and it is the slightly stronger choice. Nobody wanted that suit, which is evidence its Jack is buried rather than sitting in an opponent's hand. That Jack would be the left bower of the next suit, so calling next means one of the two top trump is probably dead and cannot be played against you.
Score Situations
Two scoreboard situations change the answer.
Opponents at nine. The instinct is to pass anything marginal, because a euchre ends the game. Resist it. Passing usually hands the call to a team that needs one point and will bid almost anything to get it, and you have to beat that call anyway. Calling puts them on defense instead of letting them pick the suit. Players who pass are not obviously wrong, but do not pass on reflex.
Your team at nine. One point wins, so call anything reasonable rather than handing the opponents a free shot at going alone. The exception is when a euchre would put them at ten.
Outside those two, the three-trick benchmark stands on its own. Adjust for your seat, not for the scoreboard.
Where to Practice
Learning Mode narrates each bidding decision, so you can compare your read of a hand against the bots' and see where you disagree. For the underlying scoring see the euchre rules, and for the loner decision that follows a call, see when to go alone.