I found some good tips and some of my own observations:
1. Dos uses this one alot: Assault class with the shotgun and you can have unlimited C4s by using the ammo crate over and over again. I don't know what level the c4 unlock come with assault. That combination is very deadly to vehicles and infantry. BTW, the USAS-12 Auto Shotgun is my new love

2. The C4 is not only good for blowing up tanks from behind, but it is also good for landmines as well. Plant C4 on a road that is often used by the opponents. Hide until a vehicle drives over it and boom! All Gone!
3. In times of heavy fire from the defender. A good thing to do, as the attacker, is to climb up into the attic in one of the houses and blow a hole in the ceiling to reach another house attic beside it. This is good for sneaking and is also amazing if you use the 1st tip I said to throw the C4 on the crate from the attic over and over again since you have unlimited ammo. There is one crate that is right below the attic hole with no ladder leading up to the attic so using this strategy is extremely helpful.
4. Use the ATV's as moving bombs. Plant C4's on the front of the ATV then get in it and drive towards an enemy tank. Right before crashing into it, get out of the ATV and detonate the C4. Bye bye tank. This is alsow known as the jeep jihad from 42 but now before doing it you must yell over TS, "LiLiLiLiLiLiLiLiLi! Die Infidel! Jiiiihaaaaaaad!"
5. I don't know if people know this or not, but the UAV does have a secondary fire if you've unlocked and equiped V Optics for the secondary weapons on vehicles.
6. Plant C4's on or around a crate right before you charge it. Charge it then hide until you see an enemy try to disarm it then BOOM!
7. The drill does harm enemy tanks in times of desperation.
8. Spot enemies for a limited amount of time by targeting their general direction and hitting the Q key. I found there is wiggle room and don't have to have your sights directly on them. I discovered this by 2 enemies in the distance both were spoted with 1 click since they were close to each other.
9. I am getting better spotting enemies. I found that planting my but in desnse foilage at the edge of a map and just observing using my peripheral vision has helped me get a sense for picking out small moves to enemies hiding in bushes. I remembered something about peripheral vision and movement so i googled it and low and behold:
"...At a few degrees away from it their density rises to a high value and spreads over a large area of the retina. These rods are responsible for night vision, our most sensitive motion detection, and our peripheral vision."
I've been trying to "stare" at the center of my screen, unlike playing in 42 where there's no cover, I would scan my monitor for enemies. In this game with the foliage cover, I found a greater need to depend on this kind of vision. Has anyone else experienced this?
10. Still learning how to "aim" the grenade launcher in hard core mode. Anyone have any tips on that? Im just doing it all by guesswork feel right now.