This is a very open ended question and the answer depends a lot on what you will take as an acceptable result. The best show car results require real first class body work which is a skilled trade requiring a lot of training and practice. Every time the metal is deformed it is changed permanently in hardness, thickness, and strengh. Managing these changes to get the desired shape of metal is what body work is all about. It isn't something that can be achieved in an afternoon in your driveway with a carpenter's hammer, bondo and a spray can of paint. That said if your standards are not too extreme, you may be able to get the fender close with a slide hammer tool then fill the rest with bondo. With a slide hammer you drill a hole and screw the self tapping screw end of the slide hammer into the hole and then lift the sheet metal back to near alignment. Sand the paint off first. Then depending on the dent you should start partway down into the dent and work it partially then go to another part of the dent and do it again. It is a problem if you pull the metal too high. Unless it is a small dent do not start at the center. You do not want too much bondo a good limit would be about 1/8". Block sand the hardened bondo with course paper because you will need to lay it down in layers.
Of course there are lots and lots of special tools and techniques to do body work and there are a lot of people reading and writing on this forum that are surely better at it than I am so do not take this as the best or only way to fix-a-dent.