Hey there Well lines are what you do when you set the pic up IE say you divide the canvas in to a grid and the choose were best to place the objects like in the top pic, Or for portraits it`s generaly a triangle you go with but any triangle shape will do say you have a person seated the head will be at the top of the triangle and the rest follows the shape it`s just a guide remember , And as a rule when you use only one object never place it smack bang in the middle of the canvas move it laft or right to give it more impact. Then you have your perspective lines which will start at the front and recede into the pic again these are just to guide you As for balance as mike said there are a few different things to consider IE lighting colours and ,say you have a tree on one side of the pic and nothing else that will full the eye into thinking the pic is going to tip over to the side the tree is on i could go on and on but mike has coverd quiet a few aspects and im sure others will also help hope it helps cheers dolly