An uneven fence is not aesthetically pleasing. It's not difficult to level a fence if a few precautionary steps are taken. With different types of fence, there are different methods to getting a dead-on level fence. The best way to level the top of a fence is with twine. For side levelling, use a carpenter's level on both sides.
Lay out the post holes according to your fence design. Do 50-foot sections at a time. Dig the holes and measure the depth by making a mark approximately 14 inches up from the end of your shovel, using the mark to measure the hole depth.
Shovel wet concrete into the hole halfway to the top. Set the posts by twisting and turning them until they bottom out. Place a carpenter's level on both sides of the post, pushing the post by hand in the direction needed to achieve side-to-side level. Let the concrete hold the posts in place. Let dry 48 hours.
Establish the height you want your fence to be, and mark it on the first and last post in line. Tie the end of a piece of heavy-duty twine on the mark and stretch it tight across to the last post in line, and tie it off on the mark.
Mark each post where the string crosses it. Using a reciprocating saw to cut all the posts off at the mark.
Lay out the fence in 50-foot sections. Mark off where you want your posts. Using the post driver, pound one post into the ground until the spade-shaped end is below the surface of the ground. Walk to the other end, and pound another post in the same way.
Stretch a piece of heavy-duty twine between the two posts. There will be white paint at the top of the post down to approximately 6 inches. Tie off the twine at the bottom of the paint line on both posts.
Using the steel post driver, drive the posts down in succession until the twine is level with the end of the paint mark on each post. Level each post side to side with the carpenter's level by bending them in the direction needed.
When levelling steel posts, don't over tighten the twine, causing the posts to bend inward. Double check your side to side level on your wood posts after an hour to make sure nothing has disturbed them before the concrete has set.
Always wear safety glasses when operating any power tool. It's a good idea to wear them all the time when working.