1/. Typically in modern, he who spots first, shoots first, and kills first. There is (rarely) any of the pew-pew-plink-plink back and forth of WW2 armoured warfare. So spotting without being spotted is so important.
2/. Therefore: He who is spotted is very likely already dead.
3/. Unless impossible, always try to place troops/vehicles in defilade positions, and hull-down. Front on-engagement are ugly, brutal and expensive.
4/. Do not bother with troops in foremost buildings: they will simply get blasted to smitherens by enemy heavy weapon fire regardless of how well hidden they are. Vice versa: any buildings on the enemy's side: destroy them with heavy calibre direct fire and deny the enemy spotting/ambush locations.
5/. Use you infantry to spot enemy missile teams, then area-fire them with support weaponry to suppress/destroy.
6. Keyhole everything, to maximise their spotting, and limit their exposure and the options the enemy has to engage them.
7/. Try to pair up missile teams without making them vunerable to the same barrage/counterfire. So if a tank is spotted, its is engaged almost simultaneoulsy by 2 missiles, ratther than just one. Hard to achieve though.
8/. And remember that your IFVs/AFV's are just that: support to the infanty (aka glorified battle taxis as well as big metal wheeled coffins). They support the infantry from hull/down defilade possitions. Dismount infantry from them well out of LOS of the enemy. Then use them to suppress potential enemy strongpoints that the infantry spot, without exposing themselves...