Do pilates and other core strengthening exercises to help you stand taller and maintain a proper posture. 

Yoga also does that and emphasizes body awareness and balance.

... and adjust your workspace accordingly to put less strain on your spine. Ensure you’ve got a chair that supports your back and is ergonomic for your workspace.

Besides your desk, rearview mirror, kitchen counters, pillows and mattresses are also things that influence your posture and need to be kept in mind.

... and more effectively, using your diaphragm. Also try breathing exercises that focus on lengthening your spine and engaging your waist muscles and lower core muscles.

Remembering to stand and sit properly is hard work, so thankfully there are apps to help us out.

Use apps that warn you when you’re slouching. 

Hold your devices properly, straight in front of you or prop it up perpendicular to the table, so you won’t be constantly craning your neck down to stare at them.

Find the ideal desk height and keep your feet flat on the floor when sitting (the right seat height is level with your knees).

... to train your body to be in the proper position, with the least amount of strain possible on your supporting muscles. But so a doctor if you have serious posture issues or pain.