How I use mulch depends upon the crop and situation. For example, I use copious amounts of coarse mulch around the bases of bananas. I just constantly add thin layers of new mulch just about monthly, not for weed suppression but as a slow fertilizer feed as the mulch material decomposes. Weed control is just a secondary benefit. The banana patches are great locations to dispose of chopped up brush trimmings and weeds. I do the same thing around taro with success, though with taro I also add some manures in with the layers. Taro responds very well to a nitrogen boost about halfway through its growth cycle.
At the seed farm I'm in the process of creating a soil base. Unlike the homestead which is moist and coolish, it is windy, hot, and dry there. And basically no soil. So mulches are heavily used there to build soil and improve soil structure. I've been using the lasagna method, layering cardboard & newspaper along with coarse material, grass clippings, pulled weeds, waste fruits, manures, soil, cinder, and sand. Where I've been doing this for a couple of years I'm actually making garden spots where taro, sweet potatoes, and beans are successfully growing. This aggressive layering method is a failure at the homestead farm. I think that's because it's too wet there. Lasagna mulching, done to the degree I'm doing at the seed farm, just results in a soggy, anaerobic mat that is slimy and smells on the homestead. Only five miles distance in difference, but this method works at one location but not the other.
So I'm going to talk primarily about mulch at the homestead farm. At the seed farm, mulch use there is a simple matter of bringing a weekly truckload of cardboard and organic debris, then piling it atop what is already there. Add water. Bingo....done. Since I can't cover the whole acre with one truckload, mulch is applied one small location at a time. Thus crops get planted into the older spots and get more mulch as it becomes available.
On the homestead farm, I'm working there 7 days a week. So I have the time to apply mulch frequently and fine tune the process. Mulching is primarily done in my food growing areas. My goals are moisture retention, weed suppression, nutrients, and overall soil improvement. My primary mulches for this are grass clippings and brush/tree chippings. I have far more grass clippings than chipped up brush.
I apply mulch by hand, one wheelbarrow or trashcanful at a time. Labor intensive, but a great workout. No need to buy a gym membership here! Applying by hand allows me to adjust the thickness of the mulch layer. Around young seedlings, maybe just an inch. Around established crops, perhaps 3-4 inches. But I have to be cautious with thick layers since grass clippings can heat up at that thickness, thus damaging the plants. I find its better to apply a couple inches, wait a week, then apply another couple inches if I'm using clippings. Coarser chips can be applied a bit thicker without the heat problem, but it depends upon the weather. If it is dry I can get away with a thicker layer than if I'm getting light rains. Since I garden year around, mulch gets applied year around, usually weekly as I mow grass.
Most of my vegetable crops get mulched. But some don't depending upon the plants and how they are being grown. Closely seeded peas in a solidly sown bed just get a very light covering of grass clippings at the time of sowing. The peas come up quite thickly, shading the soil themselves. Thickly planted leaf lettuce and radishes get none. But most crops get planted with space between the plants, giving ample opportunity for mulch. The idea is to cover the soil so that the sun cannot reach it.
When I harvest a crop here is usually some mulch still present that hasn't yet decomposed. If it's only a thin layer, then I just turn it back into the soil as I prepare the bed for the next crop. (I lightly rototill or else hand dig the bed in order to incorporate various soil amendments between crops.) If it happens to be thick, as is the case with potatoes, then I'll scoop it up and put it on an adjacent bed that is still growing. Moving it to a compost pile is simply an inefficient use of my time and effort. Old mulch very well could be added to compost, but adding it to the bed in the next row works just fine too.
I've been fiddling around with using mulch in the garden aisles. I'm not completely happy with what I've tried so far. Cardboard and newspapers tend to get slippery, posing a falling danger. Same with clippings and brush chips. Wood chops resulted in aisles that were chronically soggy, almost boggy in nature. Coarse mulch was difficult to walk on and had the danger of causing tripping. I like using cracked macnut shells the best so far, but I don't have enough of them. So I'm still working in a solution. Since the aisleways are permanent, I have been thinking of using cinders.