How much time you spend on your pile corresponds with the two basic methods of composting: "cold" composting and "hot" composting. As I've mentioned previously, the activity of the microorganisms in a compost pile generates heat and that heat increases their activity even more. When there is reduced microorganism activity and decreased decomposition, the process generates little heat and the result is a "cold"pile. This is the same process that naturally occurs on a forest floor. The organic material of leaves, needles, and wood will decay, but it may take years. If left to decompose naturally, your "cold" compost pile can take years to produce compost.
If you increase the water and oxygen available to the microorganisms, they become more active. In ideal conditions a compost pile can reach temperatures of 160F (71C) degrees. That's hot. Beyond that point the bacteria can actually die in the heat they've created. It's difficult for gardeners to have a pile that gets that hot, but 120F degrees isn't hard to do. Around that temperature organic material breaks down very quickly. This is "hot" composting.
There are two basic maintenance steps for creating compost in the "hot" method, assuming you have a good blend of greens and browns. The first is to aerate your pile. As the microorganisms grow and multiply they use up oxygen. They can suffocate themselves with an increased population so you need to ensure there is always enough oxygen in the pile. Aerating a compost pile is simply "turning the pile." With a spade, rake, or garden fork (what I recommend) you take the bottom of the pile and put it on top and take the sides and put them in the middle. You're fluffing up and mixing the material so there is more oxygen throughout.
The idea is to give the microorganisms a good mix of air and water. If you overdo it on the water, don't worry. The outer surface will dry out and the next time you turn the pile you'll be blending the dry outside with the wet inside. If it dries out a little just add water. They'll adapt to the conditions.
If you want compost fast, start with a large mass and small pieces of organic material. Turn your pile at least once a week and maintain a constant moisture level. With constant attention, your pile can turn to compost in as little as month. I've seen claims of tumblers and closed systems turning yard waste into compost in as little as two weeks. I've never seen that happen and doubt the validity of those kind of claims.
If you aren't in that much of a hurry, turn your compost every two weeks and add water occasionally. You should be able to have compost in about three months.
If you have patience or don't want to make that much effort, turn your pile once a month, add water when you think about it, and you'll have compost in about six months. If you just turn your pile a few times and wait for the rain, you can expect it to take about a year.
I suggest multiple bins or piles if you have the space. With two or three bins you rotate the decomposing material between the bins. Start with the pile on the left, add material to it, turn it, add water, and get it to the mass you are aiming for. At that point when it comes time to turn the pile, turn it upside down into the next bin to the right. While you continue maintaining it, begin adding new material to the now-empty bin on the left. About the time the right pile is ready, the left pile will be ready to turn over, so harvest the compost on the right, or move it to another bin (in a three-bin system) to continue decomposing, move the left pile to the right, and begin the sequence again. This is the basic method I use most often.
With work you can compost all year. I know a gardener who treated composting very scientifically, using a thermometer on a daily basis to check the progress of his pile. He was able to maintain pile temperatures above 100F degrees when the outside air temperature was below freezing. He'd have to cover his pile with a tarp to hold in the heat, but he was able to make compost in very cold conditions. It took a lot of effort.
I take a much slower, less energy approach. I'll do the important steps of turning the pile and keeping it moist during the growing season. At some point in the summer I'll collect the compost. I often use partially decomposed material as a mulch on the plants. For finished compost I usually add it to my garden soil at the end of the season so it has a winter to integrate with the soil.
During late fall and winter I don't make any effort to keep the pile hot; the bacteria slow down, go dormant, and stop decomposing. That's okay because they'll be ready to go when I begin turning and watering the pile in the spring. During those cold months I continue to add to the pile with all of my normal kitchen waste and any other prunings and garden clean-up. When the weather is warm and I'm back outside, there is plenty of material to form a good mass.
I am always on the lookout for composting material. I make a point to collect and save leaves in the fall. They're a great brown material. I use a leaf blower in vacuum mode and suck up the leaves. They're shredded in the process and are perfect for my pile.