It does not make a difference what plow you use or what crop you intend to plant. Simply get in your tractor, attach any plow and plow the field. Once over is all it takes and direction does not matter. This process is best left to a worker unless you feel inclined to prove you can do it. Plowing is merely to loosen the soil for the first time. It is not necessary to plow any time afterwards. Notice that you can increase the effective borders of your field and/or add fields together by pressing 'O' and enabling the plow to prepare more area for cultivation.
When adding fields or expanding them, be sure to consider how your hired workers will navigate the ends of the rows of your field. Particularly the combine. It is advised that you watch your workers operate the equipment to see what margins are needed at the edges of the field. Note that as long as you choose to run your rows a particular direction (the ends) you may plow the 'sides' of the field closely to surrounding obstacles to optimize your field size.
It does not make any difference whether you fertilize before you plant or after growth stage 1. However skipping this step will result in half the yield. Whether you use pellet fertilizer, liquid fertilizer, liquid manure (sometimes called slurry) or solid manure makes no difference. Refer to the Fertilize page for different fertilizers.
There are many kinds of sowing machines. These are sometimes referred to as drills, seeders or planters. Generally they can be broken into three categories a) Grains b) Maize/Corn along with sugar beets and c) Potatoes. Grains typically use drills and corn/beets/potatoes use planters. For each crop type make sure you are using the correct sowing implement.
Additionally, some sowing machines can also complete the cultivating step at the same time, thus fertilization would have to come after sowing. To learn which machines can do this, pay attention to the description of the implement (notice if it says it can follow a plow or if it can 'drill directly into stubble', etc.) and also the appearance of the implement in front of the sowing heads. One of the cheapest machines you can buy in the vanilla game that can drill directly after harvesting is the Horsch Express 3 TD. With this 'no-till' system, you need only drill, fertilize and harvest. Three passes over the field and you are ready to start over.
Once your field is mature and ready to be harvested, you should hop in your combine/harvester and line up with the first row of the field. Note that once your combine is running you may press 'B' to start your 'harvester' (the head of the combine) and lower it to the ground (doing both steps at once). As you run through the field, it will start to cut the crop and leave the remains of the plant that is not seed (sometimes also called berries) on the ground behind the combine.
If your grain platform is moving but you are not harvesting the plants, they may not be ready yet (navigate the 'ESC' menu to check the maturity of the field) or you planted a crop that you cannot harvest with that machine. Note that your starter combine can harvest anything your starting sowing machine can plant aside from grass, of course. Likewise, if you press 'V' it will raise the platform but leave it running. This is useful at the ends of each row as you maneuver to the next row without dragging the platform on the ground; potentially making turning difficult in bumpy terrain. Once you are lined up again, just press 'V'.
Most farmers will hire a worker to operate the combine once it is running in the first row and operate the tractor (with trailer in tow). As the combine fills its bin, the hired worker will raise the pipe (toggles with 'O') at 80% capacity. This is your cue that you need to pull the wagon up under the pipe and the combine will automatically dump the harvest into the wagon. Note that the starter combine has a dreadfully low bin capacity and you will need to babysit the combine with your (dreadfully low capacity) wagon. To facilitate this unloading process without crashing into the combine or continually going too fast or too slow, use '4' to set your tractor to the harvesting speed. You may also choose to stay side-by-side with the combine for a time and it will continually drops it's yield in realtime into the wagon.
Note that you start with the grain platform for your combine. This will harvest wheat, barley and canola. A better combine will also have the corn head available which will allow you to harvest corn. This is why you will see two heads for the better combines. Both potato and sugar beets have their own harvesting equipment. Note also that if you wish to harvest silage from corn, this is yet another machine. The silage chopper machine takes in the entire corn plant and chops it up for feed whereas the corn head on a combine merely separates the corn kernels and drops the rest of the plant back on the field.
If you wish to gather the straw from your crop, you may do so. This is useful for feeding your livestock with a total mixed ration. Be aware that the stalks left behind a combine from your wheat & barley harvest are what yield the straw and mown grass yields hay (once it has been tedded and optionally collected into windrows). Also, some mod harvesters employ choppers which chop up the stalks for those that do not intend to bail the straw. If you are not seeing stalks deposited behind your harvester, you must turn the chopper off.
Note that a forage wagon can also pick up the remains from your combine directly.
After the crop has been harvested (and after you have gathered the straw if you choose to do so), you must cultivate the remains of the crop into the ground. This prepares the soil for a new crop to be sown (or planted, etc.) Some sowing machines will complete this step at the same time, thus saving this step.