Step 5: Tear Down the Old
Tearing down the old fence is a pain, but it also should go quickly. More than likely the wood is old and worn down, which means it probably won't take much to knock it over. Make sure you pull out the old posts, concrete and all.
Step 6: Getting Started
Decide on how high you want you posts, then at one end of the fence tie an end of the string line at that height and do the same at the other end. Make sure that the string is tight. Now, all of your post should be right at that height so go ahead and concrete them in.
Do the same with you 2x4's, make sure you decide on how high you want each one to run and make them flow along with the string. Then do the same for when you are putting in the fencing slats.
Using the string line will ensure that your fence has a nice flow to it and it will look even and level through out. Understand that the ground will not level, so using the string line will help.
Step 7: Make Your Cuts
Cut the tops of the posts to where they are even with the string line. The easiest way to do this is to use a saws all. You can rent one from the Home Depot for fairly cheap since you will only need it for one day.
After your 2x4's are run, it's time to start running your slats. The best way is to take the slat and see if the top is even with the string line and then look and see how much room you have at the bottom. You do not want your wood to be touching the ground because that will cause damage, but you also do not want a huge gap. 3-4 inches from the ground is always good.
The best way to make your cut is to flip the slat upside down and make your mark at the bottom of the slat. The make your mark where the string line is touching the wood. Use the circular saw to cut the slat and then your ready to screw it in to the 2x4's.
Step 8: Enjoy
The process can be slow and physically demanding at times but you will enjoy the reward of putting up the sturdy fence yourself when you see the results. Hopefully you had help but this is a job that can be done on your own.