My favorite source on this topic: How to Practice CS:GO
I'd add that nowadays you can download maps like training_aim_csgo from the Steam workshop and I've found them useful for practicing specific movements.
Also, helpful console commands and such: Practice Configuration & Binds for Local Server

Some newbs look at the ground when running about. Instead keep your crosshair where your enemy's head might be so you don't have to move it as much when you see someone. More here: CSGO Crosshair Placement Tutorial