Next to my monitor I have a colour correct print viewing booth that allows me view any prints or proofs.
This particular booth has variable intensity lighting which allows me to match the brightness of the monitor by turning the silver knob on the top side.
By having consistent colour and brightness between my monitor and the booth it makes it easier to check that the image on the screen matches the print image and makes correcting proofs easier.
Print viewing booths are essential for viewing CMYK proofs – especially contract proofs as it is assumed that they will be viewed in this standardised way.
They can be expensive to buy (particularly variable brightness ones) so they are an optional buy if budget is tight, if this is the case then a separate Ottlight will be cheaper and can double as a behind the monitor light.