Making a left hand turn as a commuter
What you do strongly depends on the road layout:

There is a dedicate bike lane
Stay on the bike lane and, if it also goes to the left where you want to go, follow it. Avoid cutting corners just to shorten your way and signal in time your intention (also other fellow cyclists prefer to know where you are going in advance). If the lane doesn't turn left where you would, follow next point.

You drive in the normal traffic
The normal procedure to turn left (assuming you ride on the right) is to get to the center of the lane and then turn as soon as no vehicles are coming from the front. Therefore put your left hand out in advance and make clear you want to move left. Wait some time with the hand out, check that no vehicles are approaching at your left and slowly but steadily move to the left. Complete the turn as soon as possible.

Alternatively, cross at a pedestrian crossing (dismounting from your bike if necessary).

In all cases:


Be visible: wear high visibility gears. Bikes are small and easily slip past consciousness in traffic.
Be assertive with your movements and don't zig zag. You don't want the drivers to assume you are just erratic in your cycling.
Listen and read the traffic. Learn to understand the context around you: are the drivers calm? Do you see anybody who is distracted or plainly a jerk?
Don't wear headphones or fiddle with your smartphone while cycling
Be fit and avoid cycling if you are not in condition of doing it. You want to be sure you can react promptly on the road
last but not least Safety first