Shift + move arrows will move the objects in predefined increments of half a grid length along one axis. Moving with cursor arrow gives you a quarter of a grid rectangle. alt+move is free moving. For turns, one click on Rotate while holding shift means 45 degrees. Then there's Align options in Edit menu. Snap Together will bring the centres of objects together. BTW, see that magnifying glasses beneath the wireframe cube in the lower right corner of the screen? Need I say more? :-) The default is centering on the selected object in parallel views, but you can use the hand to move the screen along.

-- erlik