I suggest you read, read and do some more reading. It is all here and everyone does it differently. Look at the very first sticky on the DIY section and then ask questions in the right hand search box.
There are no laws with this. It is a personal preference thing. I'm a 10% dilution blender, others are 20%, others are neat and then dilute. It depends how much you want to use up of your valuable essential oils and abs whilst experimenting. I think things smell better on the nose at lower dilutions when blending, but that is only my opinion.