Installing fence posts seems, at first glance, to be a no-brainer. When you seek to actually accomplish the task as an amateur, however, you learn the frustration involved. Have no fear, though: When you understand the proper procedure, setting your fence posts will be easy and effective. You will need a long string, a can of spray paint, a measuring tape, a vertical level, a digging bar and a shovel. Also useful will be some ready-mix concrete, posts, and possibly, if you want to get fancy, some post brackets.
Lay your fence line
Tie a string tightly between the two end points of your fence span. this will create the straight line you need to work with when placing the posts.
Mark your post locations
Measure your total span. The length of your span will determine the number of posts you will dig. divide the total span by 2 to find the exact center of your span. Use your spray paint to mark the spot under your guide string. Begin dividing the spaces in half until such point as you have no spans that are greater than 6 to 8 feet. Mark each post point with spray paint on the ground as you move forward. When done properly, the center of your paint mark should always sit on the span length center as well as being centered on the string line. (Note: When laying multiple fence lines that intersect, use your longest span to determine the distance between posts and then use that distance everywhere except for the end pieces which will need to be a custom length)
Dig your holes.
Remove your guide string and begin digging post holes in the spots you marked in spray paint at the ends of your span. Typically, you will dig post holes about 18 inches deep. If you plan to let the concrete free form, be sure to dig your hole 8-10 inches wider than your posts. if you are using forms, dig until your forms sit neatly in the hole you dig, tops flush to the ground. Dig the two holes at the end of your expanse first. The others will come later. If using forms, use your level to make sure the forms sit level in the hole.
Place your first two posts
If you are using forms with brackets, mix your cement, pour it, and place the bracket tail into the cement and wait for it to dry. Once the cement is dry, you can use your level on two perpendicular sides to establish a true vertical angle before screwing the post into the bracket. If you are using free forms or dropping the posts right into the concrete, drop the post, level it using wood braces to keep it level during pouring, pour your cement around the post and then re-check that it is true vertical before letting it dry. (Important: Make sure your posts are long enough. If you are building a 6 foot fence, 6 foot posts will only serve you if your posts are in brackets above ground. You can always trim off posts that are longer than you need, but you can never add to posts that are too short)
Tie your guide lines
Using string, once your end posts are dry and secure, tie, a string between the two posts, about 8 inches off of the ground and again toward the top of your post. Be sure that your string runs along the same side of each post for both the top and bottom strings. Use your edges. Don't try to center the string. Make sure the line is tight enough that the strings run in a straight line.
Add your remaining posts
Dig your remaining post holes in the locations that you marked previously, using the same instructions for placing your forms and posts. When installed, your posts should touch the guidelines along the top and bottom without leaning on those guidelines. Make sure to use your level on perpendicular sides to keep the posts level as you go.
Properly seated fence posts are the most important part of building fencing. Be sure to pay extra attention to these steps and may your next fencing project be a tremendous success.