Installing any fence requires that you use solidly installed fence posts to connect it to. Setting your fence posts in concrete ensures that the post is there to stay, resistant to movement by anything but the strongest of directly applied force. Setting a wood post properly though, requires that you do more than just dig a hole and pour in the stone. You'll have to follow the correct procedure, creating a proper bedding for the concrete, as well as using an amount that's sufficient for holding the pole in place while not wasting concrete in the process.
Dig a hole for your fence post of up to 6 inches in diameter that is 12 inches in diameter and 24 inches deep. For larger diameter posts make sure the hole you dig is at least twice the post diameter. Dig a larger hole if the area for your fence post experiences high wind or heavy water flow.
Pour a layer of gravel into the hole measuring 6 inches in depth to serve as a drainage bed for water that seeps into the hole. Draining the water into the gravel prevents standing water from wet concrete rotting the base of the fence post.
Paint the bottom of the post that sits in the hole with an asphalt emulsion to provide a waterproof layer between the post and the concrete. Measure a point on the post that is 19 inches from the bottom and paint the post to that level so that one inch of the painted wood rises above the concrete once it's poured. Allow the emulsion to dry for an hour before planting the post.
Place the pole into the hole. Purchase a fence post that's 2 feet taller than the fence in order to have enough room to bury the post and adjust the height afterward. Secure the post in place using wooden stakes and two-by-four pieces. Plant the stakes into the ground 3 feet from the post to either side, planting them securely using a hammer. Cut the two-by-four pieces so that they lean from the stakes to the post with the post centred. Nail the two-by-four pieces to both the post and the stakes, checking the post for vertical plumbness using a carpenter's level as you do so.
Mix the concrete with water in a wheelbarrow using a hoe, following the manufacturer's instructions. Pour the mix into the hole until it's even with the surrounding surface, filling the hole and securing the post into place. Allow the concrete to set according to the time suggested by the manufacturer. After the concrete sets, you can finish the fence installation to the post without knocking the post out of position.
You can substitute quick-setting concrete for speedier installation of the fence posts.