There isn't really a way to obtain fair skin quickly, but there are a couple of methods that will certainly work over time. Here are the best options.
Cover your skin
Going outside in a t-shirt and shorts is a great way to get a tan, but it's not going to help you obtain fairer skin. Covering yourself up when you're out and about will stop your skin from tanning. Over time, any tan that you already have will start to fade away to your natural skin colour.
Exfoliation is a great way to make your skin fairer over time. Exfoliation is the process of removing dead skin cells, and of course, over time you'll be removing layers of tanned skin cells, leaving a fairer tone underneath.
The above methods are the best way to make your skin fairer over time. Some people recommend that you apply lemon juice to your skin as it will help during the exfoliation process, but this may simply be a myth.