The answer to this question depends on the level of the officer and the job he is expected to carry out.

In general, the lower your rank the closer to the guns youre going to be. Officers commanding units up to the brigade would be deployed in extremely forward positions. Lieutenants, captains, and majors would all travel with their commands, while colonels and brigadiers might be expected to move from one command to another, ensuring that the operation, either offensive or defensive, would be carried out according to their wishes and the wishes of their superiors. This might put them at the vanguard of an attack, and many brigade commanders in World War Two would mount up and lead their men from the front. But this could also mean moving back into the rear areas, directing traffic, and ensuring a steady supply of men and materials arrived at the front.

Divisional commanders and above often became gradually removed from combat. Their job was not to coordinate the movement of troops per say, but the movements of commanders. They ensured that their orders were being carried out, that commanders were moving effectively, and that they understood properly the situation on the ground. Thats not to say that they didnt see combat or experience danger, may of them did and many were killed. But often times the job of the general officer is to move around from headquarters to headquarters coordinating action, rather than from unit to unit compelling action. As a result, many of these officers traveled in cars and jeeps, soft skinned vehicles, as well as planes, rather than tanks.

At the lower level, commands could be relayed a number of ways. The most obvious and effective (at short ranges) was by voice. A Lieutenant might shout orders at his men, while his superior might send a courier to hand deliver verbal or written orders. A number of other, more indirect methods were used to also coordinate movements, including whistles, flares, smoke, signal flags, or other visual methods. One of the major developments of the late-interwar period, however, was the miniaturization of the radio. During World War One, radios were too large and sensitive to be carried into battle. But with the advent of man-portable radios, soldiers of smaller units could communicate effectively with other units and their superiors beyond visual range. This was especially important in coordinating with multiple combat arms, such as air power, infantry, and tanks. One of the key German innovations in 1940 was that each of their tanks had a radio inside of it so that commanders could communicate with each other, giving them an edge over the allies who still relied on visual and verbal communications. At increasingly higher levels of command, fixed command posts and headquarters were established which had an increasingly large number of staff officers and communications equipment. Headquarters which could be established in fixed locations could be strung up with electricity, telegraph lines, and ground based means of communications. These communications had a number of advantages over radios. Especially important was that they could not be easily severed (to cut a telephone line, you have to physically cut the line) and they were not easily intercepted by enemy intelligence agents. Units, especially brigades and higher, would have a sophisticated communications network which would monitor its constituent commands as well as those of its superiors and its neighbors, using a mixture of land lines, radio links, and the trusty courier to deliver reports and orders.

At the higher echelons of command, these headquarters could become quite large themselves. Think, an American armored division had two combat commands, so two direct combat commanders underneath the division commander. But it also had a number of constituent battalions which may or may not, at any given time, be attached to either of the CCs. In addition, the division would have organic artillery units, anti-tank units, and anti-aircraft units. But those are just the 'line' battalions. A division would also have a motor pool, transport companies, medical units, mobile garages and workhouses, penal units, food services, etc. To manage all these different organs a headquarters employed lots of staff. But then these staff needed commanders and managers to coordinate their activities to ensure it fit with the divisions larger mission. Thats a whole different conversation, however.