The term shoot and scoot refers to an artillery tactic of firing at a target and then immediately moving away from the location where the shots were fired. The reason for this is to avoid counter-battery fire - shots fired at the origin of incoming artillery by the enemy, in order to suppress and/or destroy the battery or batteries.
Shoot-and-scoot tactics require fairly mobile artillery. It is difficult with towed guns, as the time required to break down the guns and hook them up to the transport vehicles then drive away is significant and by that time counter-battery fire may already be falling on the position. In this respect, rocket artillery like the US Multiple Launch Rocket System (MLRS) or Soviet Katyusha is superior as all the rockets can be fired in a short period and then the launching vehicles can be driven away almost immediately. Self-propelled guns (such as the US M109 Paladin or Soviet 2S1) can also use this tactic but they can only fire a limited number of shots (due to their slower rate of fire) before moving on, and may require some time to retract jacks and such which afford them stability while firing, before they can move.
A well organised battery or batteries might survey a number of suitable launch sites when they arrive in a battle-zone and practice their shoot-and-scoot tactics between them. This makes their movements a little more predictable, but allows them to arrive in a suitable launching zone quickly after one attack so that they can be ready for the next as soon as possible. They could even make provisions for shelter and/or camouflage at each location.
The number of shots fired before moving on would be determined by the range they are firing at and the quality of the enemy's counter-battery radar (or other spotting techniques), which determines how quickly the counter-battery fire can be fired against them.
See also: Artillery (Counter-battery fire)