Layout of your fence. The basic theory is that you stake out where your fence will be and stretch a string between them. This will be a guideline when you are installing the posts. If your fence starts with your house you will probably like to have it at a right angle. It is a simple procedure to get this right. First stake the spot where you like your fence to start. Fasten a string to the stake and stretch it out roughly perpendicular to your house. Measure out 1,5-meter out on the string and mark it. Mark a point on your house one-meter from the stake. Hold a tape measure diagonally between the one-meter mark and the 1,5-meter mark and move the string until the distance between the marks is 2-meter.
Tie down your string at this place, and it would be perpendicular to the house. Mark the position of your first spot, then measure out for the line to mark the rest of the posts. Thee string should be at the outside of this post, so you have to measure in from the string for center of the posts. Mark this with a stake so you can see them. If your fence goes down hills you have two choices, you can have top of the fence to follow the slope of the hill or you can keep the fence sections level and step the fence down at each post. If you like to have step down fence, estimate the height different from top and bottom of the hill and divide this number by number of sections. And you will get the amount to step the fence down at each post.
Digging holes. You can use a clamshell digger to dig your postholes but this is a very hard fork and if you got plenty holes or you have hard ground it could rent a power auger but you normally have to be two people to run it. In most areas you need to have the postholes below the frost line to make sure that the post will stay in place when the ground starts to heaves due to the frost. As a guideline you should bury about half of the corner posts and about a third of the line post underground.
Setting posts. It’s a good idea to put a 30-40cm layer of gravel at the bottom of each hole to prevent rot and decay. The gravel will allow water tat collects at the bottom of the hole to drain away. Set the end post first and line up the post edge along your layout string. To prevent water from running down between the post and the concrete you should fill the hole little bit higher than the ground and slope the top of the concrete away from the pole a little. Brace the post in place while the concrete cures. The line post doesn’t need that much support. Normally it’s enough to set them with dirt. Use a spacer to get a consistent distance between them and shovel dirt around them when you have the posts in position. When you have 15 cm filled with dirt pack the dirt down and keeps filling it up. When you have all posts set hard, trim of the tops to get proper height.