1. Double. This tells partner that you have the values for an opening bid and support for the unbid suits. With excellent holdings in both majors, the double is preferable to overcalling with one notrump, which is a reasonable alternative.
2. One diamond. This is somewhat of an underbid, since an overcall on the one-level more often than not denotes less than an opening bid. However, a takeout double to show your high-card strength is not an option, since your partner might respond in hearts and create an insoluble problem. (Retreating to two diamonds if partner bids one heart would show a stronger hand – usually 17 or more points.) If the bidding develops favourably, you plan to bid spades at your next turn and in that way belatedly show both the strength and distribution of your hand.
3. Three spades. This is a preemptive bid pure and simple, and indicates a weak hand with long spades. It is essentially an effort to deprive the opponents of bidding space and make it more difficult for them to reach their best contract.
4. Double. This should work out better in the long run than one spade, which is the alternative bid. In such situations, you weigh the advantage of doubling and possibly finding a heart (or diamond) fit against the advantage of overcalling with one spade. A majority of experts would favor the double.
5. Four spades. This leap to game combines the virtue of pre-emption with a legitimate chance of making the contract. The jump to four puts a lot of pressure on the opponents and could cause them to make the wrong decision.
6. One notrump. This is by far the best way to describe your hand. True, you have the high-card values for a double, but with only five cards in the majors, notrump is the better choice. The notrump overcall shows 15 to 18 points, balanced distribution and at least one club stopper. That’s what you have, and you can deliver that message in one fell swoop.