It can be a post for a mail box, a flower pot holder, a fence post, or even a clothes line. Yep, people still have these and if our energy bills get any higher we may all go to using them.
First make sure you have the right post for the job. It can be metal or wood. For wood, make sure it is Pressure Treated and rated for ground contact. Different pieces of lumber have been treated differently, and not all are rated for ground contact. Metal can be Galvanized, such as used for chain link, Aluminum, and Iron. Pick the most proper one for your use.
Next is the hole itself. The shape is just as important as the size. All post holes should be bell shaped. That means wallowed out wider at the bottom than the top. A'la - Bell Shaped. This prevents heaving when the ground is frozen. Heaving is the frozen ground tightening around the post and forcing it toward the path of least resistance - up and out of the ground. The wider part, the bottom of the bell shape, will be located deep enough in the ground so it is past the frozen part and therefore will hold the post during the freeze / thaw cycle. This is the main cause when you see a Fence Post leaning over. The post were not set correctly. To wallow out the bottom of your hole simply take your post hole diggers and chip away the earth from the sides near the bottom of the hole. It does not have to be much wider at all - just slightly wider than the diameter of the rest of the hole is enough to do the job. Remove all loose dirt from the hole. Next, using a tamping bar, tamp down the bottom of all holes, making a solid, hard packed surface. This will prevent any settling effect from the weight of the posts and concrete when placed in the hole.
When determining the post hole size and depth, Click the Link, located below this article and use the table to determine the size of posts needed for the type and size of fence you are building. For most other applications, mail box posts and so forth, a basic 4x4 (PT) will suffice. Make sure the sides of the hole are smooth and cylindrically shaped. We dig most of ours with augers, however we still use post hole diggers quite a bit. Fill the bottom with approx 3 to 4 inches of gravel to promote drainage. This is very important. Most people do not know it, but concrete is a very porous material. Being porous is the main cause of concrete driveways cracking. Water soaks into the concrete and the freeze/thaw cycle will do its job and crack the concrete. To avoid this cracking around a post, put the gravel at the bottom. This helps to keep the post and concrete well drained.
Mix concrete according to the bag directions. In general, concrete must be well mixed. Do this with short handled spade in a wheel barrow. For small amounts you may use a plastic five gallon bucket, and a small garden, hand spade. If your are not a pro, only mix 1 bag at the time, wheel barrows are easier to turn over than people think. Mix the concrete to a mashed potato type consistency. It should pile up on the shovel. Take care not to mix any dirt in with the concrete as you are working it, or pouring it. Dirt weakens concrete substantially. Level your post and shovel the concrete in the hole to about 4 inches from the surface. If possible leave the hole open for a day or two to help the concrete dry, then cover it with dirt. In the winter time we use a special additive to help in drying of the concrete.
Posts can be set with dirt alone, although you must tamp, tamp, and tamp some more to get it set really firmly. All Western Red Cedar or White Eastern Cedar post must be tamped in as concrete will cause the post to rot, and should not be used. Dig the hole the same as above, put the post in and level in all directions. Add a few inches of dirt then tamp down soundly, add a few more inches and tamp down again, continue this process all the way to the top. If you tamp hard enough that post will be set as good as in concrete.
Check this Link out to see our Fence Post standards!
It tells you the size of post to use for the fence you plan to build. It also tells you the diameter of the post hole and how deep it should be.
Link for Post Depths for the size of Fence you are building!
Getting a new roof is not a big job, well it's not a big job if you're not doing it. Whether you are completing your own roof job or hiring a contractor, theres a few things to know about roofing. If for no other reason than to know it is being completed correctly. The first step of Roofing is installing the underlayment. Most notably Felt. Felt underlayment acts as a water proof barrier between the roof decking and the outer roofing material. 
First make sure you have the right post for the job. It can be metal or wood. For wood, make sure it is Pressure Treated and rated for ground contact. Different pieces of lumber have been treated differently, and not all are rated for ground contact. Metal can be Galvanized, such as used for chain link, Aluminum, and Iron. Pick the most proper one for your use.
When determining the post hole size and depth, Click the Link, located below this article and use the table to determine the size of posts needed for the type and size of fence you are building. For most other applications, mail box posts and so forth, a basic 4x4 (PT) will suffice. Make sure the sides of the hole are smooth and cylindrically shaped. We dig most of ours with augers, however we still use post hole diggers quite a bit. Fill the bottom with approx 3 to 4 inches of gravel to promote drainage. This is very important. Most people do not know it, but concrete is a very porous material. Being porous is the main cause of concrete driveways cracking. Water soaks into the concrete and the freeze/thaw cycle will do its job and crack the concrete. To avoid this cracking around a post, put the gravel at the bottom. This helps to keep the post and concrete well drained.