Best time to move Amelanchier Lamarckii shrub

It depends how big it is and how well established it is. If it is quite small you could move it anytime now whilst it is dormant. Dig around it with as much of a rootball as you can manage to move. Have the receiving hole already dug so that it is out of the ground for as short a time as possible. Water it in well and continue to water occasionally throughout winter and during dry spells. Water regularly for the first summer. Good luck. This shrub likes clay soils.