This subject is super in depth and it is best to take a course, do a workshop or training to really understand how to style your clients correctly. however i am going to share some basics with you to help in particular those new technicians and those who have never been taught basic styling.
so predominately it is the eye shape we focus on however we also do need to take into account the brow shape, face shape, whether they are close or wide set etc. so in the post i can not go into detail as there is too much info so we are going to focus on the basic different styles you may hear and whom they might suit.
dolly - this is great on young clients in particular as they tend to have stronger and longer lashes or those who want lashes to be long throughout the lash line. in dolly styling you use length over a large proportion of the eye and quickly graduate down in length on the inners and outers. this is also good for a client who has wide set eyes.
rounding - this is whereby you place the length over the iris, so roughly it is the middle of the eye. this is a great style on the more mature client or those who have a hooded lid or are wide set as it will draw the eyes closer together. *continued in comments below*