To properly strike in the bagpipes, they need to be brought up to pressure very quickly.

First, hold the bag out in front of you.

See the pictures from the side, you'll notice that the bass drone is balanced horizontally on the shoulder, the bag in front of you. The left hand is holding the note "D". (Note: if playing with a group, it should be the note "E" but it was late at night and I couldn't wake my neighbors)

The right hand is on the bag.

The bag is resting against the bones of the forearm, and if you consider the right palm to be the hammer, the left forearm is the anvil.

At the moment right before the drones start to make sound, you push with the right hand quite suddenly, like a strike. But is should not appear to your audience as if you were striking your bag.

At the same time that you are pushing, you are blowing a puff of air into the bag.

If all this is correct, all your drones should come up with no wailing or silence from any of them.

Continue to blow so that the pressure remains steady, and gradually remove your right hand, tuck the bag under your arm, and place your right hand in the position to play the note "E" which should be the note played when you then bring the bag up to full
pressure to make the chanter sound.

From this note "E" you begin the tune.

Now if you are playing with a band and it has a bass drum, the first two beats of the lead-in on the drum are when you inflate the bag, the third beat of the lead-in is when you strike in the drones, the fifth beat is when you bring the chanter in, and the tune starts on the sixth beat of the bass drum's lead in.

Have a listen to a band striking in on a recording and you'll see how all this fits together.