Rule1: Thinner clothes first
Make sure to start with items that are made from thinner fabrics such as a cotton T-shirt, dress shirt or turtleneck, and then layer them with heavier items such as a wool sweater, a corduroy blazer, or a leather jacket.
Rule 2: Define the layer
A layer is essentially any item that can be worn on its own and look great. In other words, wearing a tacky wife beater underneath a stylish dress shirt does not qualify as cool layering.
Rule 3: Keep it casual
Layering is best used for casual occasions and is generally not appropriate in more formal settings. Keep in mind, however, that a layered combo can include one or more classy pieces, such as a tailored blazer and a fine dress shirt.
Rule 4: Always feel comfortable
Don't wear anything that feels uncomfortable. With that in mind, if you can't move normally then your layering combination is most likely too thick and therefore, far from trendy.
Rule 5: Mix in some color
Be fearless and don't hesitate to spice up your look with a little color. Remember that combine it properly.
Rule 6: Layering is practical
Prefer wearing two or three thinner layers of clothing rather than one thick one.
Rule 7: Jacket not required
Last but not least, remember that layering must not necessarily include jacket.
Now that you're informed with the rules layering, it is all up to you to put them into practice.