Where does the trump card go after I pick it?

It is placed face down on the table. It returns to your hand when the trump is revealed.

Nobody, until someone who cannot follow suit asks for the reveal. Not even your partner.

How do I pick the trump suit?

Choose the suit where you hold the most high cards, especially the Jack and the 9, and where your partner is likely to help.

Can the trump suit change during a hand?

No. Once it is set, it stays for the whole hand.

Should I choose a suit with only one high card?

Usually not. One high card in a suit can be trumped or lost, so pick a suit that gives you several winners.

Who should lead when trump is set?

The player on the dealer's left leads, as in most versions. Lead trump only when it helps your plan.

Choosing a trump in 29: the suit that wins the hand

You have won the bid. Now comes the decision that will decide whether you make it: which suit becomes trump. In 29 the trump stays secret until somebody runs out of the suit that was led. The choice is part strength calculation and part bluff.

The face-down card

After winning the bid, the bidder takes one card from their hand and places it face down on the table. The suit of that card is the trump. The card is out of play until the trump is revealed, and then it goes back into the bidder's hand.

Nobody else knows the suit. That includes your partner, who will find out the same way as the opponents.

Length first, power second

A trump suit does two jobs. It wins tricks with its high cards, and once the other trumps are gone, it wins tricks with its low cards too. The second job is why length often beats isolated power.

Three cards of a suit that include the 9 and the 10 are often a better trump than a lone Jack in another suit.
Four cards of a suit make a trump almost regardless of rank. After two rounds of trumps, your 7 and 8 start winning tricks against point cards.
A Jack and a 9 together in one suit is the ideal. Choose it even if another suit is one card longer.

Which card to put face down

Put down a low card of the trump suit. The card is unavailable until the reveal, and you want your Jack and 9 in your hand, ready for the first round of trumps. Do not hide the Jack unless it is your only card of that suit. If it is, you have probably picked the wrong suit.

When to ask for the reveal

The trump is revealed when a player cannot follow suit and asks for it. If that player is you, think before you ask.

Ask early when you hold the long trump suit and want to start pulling trumps out of the opponents' hands.
Hold off when you are short in trumps and the opponents would benefit more from knowing the suit than you would.
Once the trump is revealed, any player who cannot follow the led suit may trump. Before the reveal, nobody can.

The defenders face the same choice. A defender who cannot follow suit and does not ask for the reveal can discard a losing card instead, which keeps the bidder guessing for another trick.

Reading the bidder's suit

Even before the reveal, the trump leaks out. A bidder who leads hearts twice and never touches spades is often protecting the suit they chose. If you hold a single card of a suit the bidder keeps away from, keep it. It may be your way into a trick later.

The same four cards as a trump: length, the Jack and the 9 together.

Mistakes that cost game points

Choosing the suit of your single best card instead of your longest suit.
Putting a point card face down, where it sits useless for the first three tricks.
Asking for the reveal with two trumps in hand against a table that is clearly long in the suit.
Forgetting that the face-down card comes back to you. Count it when you plan how many trumps you hold.

The choice gets easier after a few hundred reveals. 29 Royale shows the reveal with a short zoom on the arena floor, and the tutorial explains the trump the first time it is turned over. 29 Royale is free on Google Play if you want those reveals on your own table.