Enlisted is about decisiveness, NOT careful planning. You have to use your instinct to make swift decisions - frontal assault, flanking, or cutting enemy reinforcement? Do you continue your friendlies' direction of attack, or do you open a new flank?
Therefore, it is fatal if you waste your time building fortifications for your rally. A rally barely concealed and not covered erected before the enemy is ready, is infinitely better than a late rally that is overly covered by sandbags. You can have a completely exposed rally, if judging by the map, your ear and the sounds, the enemies are completely unaware of your operation - that rally will capture the next point, because, a squads of friendlies will be born from it and join you to take the next point before the enemies are still raging for the previous point.
With the above understanding, the most important factor of rally building is NOT the physical environment. It is TIMING. You have to be fast, and ideally unexpected. If you hear enemy rally nearby, forget it. Destroy enemy rally before building your own. Do NOT be a perfectionist in finding the best place or building the best fortifications for your rally. You are wasting precious element of surprise!
When NOT to build a rally:
The purpose of a rally is to FASCILITATE the objective. It is an improvement, NOT a necessity. If you are a defender, you are just born from the default spawn - 150m from the objective. The enemies are already in the objective overwhelming your friendlies. You are the only closest reinforcement. The right thing to do now, is NOT to sprint to 100m and to build the rally. The right thing to do, is to hold your katana (or whatever fastest weapon for sprint for your faction) and sprint directly to the point!
There is already a friendly rally UNDER 100m from the objective. There is no overwhelming enemy firepower preventing assault from that direction. Then USE your friendly rally if it is immediately available, and assault the point directly. Do NOT waste time and build another rally - even it will be closer to the objective.
Your default spawn is already below 100 meters from the objective (typically the Normandy beach map), and enemies are imminent against your point - a bunker. Do NOT build a rally. Get inside your bunker and if possible, build a sandbag on each of the steel door.
Wrong ways to build a rally, and the right corrections:
You are LEADING your entire team in pushing for the next objective, frontrunning your enemies. You have stopped to build a rally. After taking that significant amount of time. You have decided to waste MORE time to build sandbags and even barbwires to protect your rally. WRONG! Just build the rally behind a bush, or a shallow cliff, and MOVE ON!
You have built a rally inside a house in Normandy. It's somewhat concealed and covered, but imperfectly. You have therefore decided to put a f_cking sandbag ON the window, announcing to the whole world that where your rally point is. WRONG! Take the imperfection and MOVE ON! The best cover for your rally is keeping your enemies preoccupied by your assault!
Eastern Front: You have cleared a house on your way to your objective. It's equal or under 100m from the objective, so a good distance for a rally point. You could have just built the rally on the first floor. Instead, you have decided to go to the second floor, then you see an attic, and you take your sweet time to climb the attic, and then you build your rally there. Not content of wasting so much time, you have then built 3 sandbags in front of your rally point, making the bots of your teammates near impossible to get out. And when they DO get out, they go out one by one very slowly, to be mowed down by the superior enemy number. WRONG! Build your rally on the FIRST FLOOR! If it is unacceptably exposed, Put ONE sandbag in front of it INSIDE the house, and NEVER on the window!
Right way to build a rally:
Be swift. Be first. Build your rally at or under 100m from the objective. Use natural concealment and cover as much as possible. Do not carry a spade. It is a total waste of time to dig. I always carry a katana or an axe for quick movement (katana is 150% sprint bonus), or in case of close quarter combat - when the enemies are on the other side of the wall.
If the element of surprise is yours, then concealment or cover does not matter for your rally.
If the element of surprise is gone, then build your rally with ADAQUATE natural concealment to keep it out of enemy's direct line of sight. If no such natural concealment is to be found in a reasonable amount of time, Build a sandbag and pray that enemy tank does not blow it to smithereens.
