There is some exploring to be done in BF3, most of it is bannable.
First, take out your UAV (I know its real name, but I'm avoiding google searches). Jump on it. Stand in the center. Now fly it directly upwards and you can use it exactly like an elevator. The bad news is that most of BF3 either has an invisible ceiling or invisible walls. There are lots of places that you can get to though. One example is the upper levels in the RU deployment room on METR0. If you AC 0G snip e from up there you can have a good ol time.
Second, legitimate spots from which to camp.
METR0- It is possible to get on all the locomotive cars (again, google searches).
Orienting North as C and South as A:
North East most locomotive you can jump on the trash cans. This one is fun because you can hide behind the smoke but still see snipers at the end of the tunnel that are using 8x or 12x, its a waste if you are using that scope btw. You can also get on the door that is near by and lay down, giving another swell spot.
For the unit that is South of the above mention: there is a burning loco right by C. If you shoot out the window of the Southern unit, the one facing the burning pile, and jump on the dash of the loco. Turn around and jump on the end of the burning loco car. Then jump back. Great position for a support to hold down the front stairs.
For West of C:
North West, go all the way to the back of the US deployment and jump up the embankment. Then turn and jump onto the wall of the burnt out car and crawl across. Getting to the next car takes some practise but can be done. Great position if you are getting camped. Also completely worrthless is you are going to use a 8x or 12x scope.
West: Go into the burning car and towards the North end (using the previous orientation). Jump towards the drivers compartment from the right side. You'll get the jump over animation and end up on top of the wall (some times). From here you can get onto the top of the other cars or hide in the smoke to camp. Again, useless if you are going to use a 12x or 8x.
Of course, you can use you UAV to get on top of almost all vending machines.
South end of map (assuming A is South and C is North): if you go to the second story of the building due East of A, the South side, second floor you can jump on the awning. Run and jump to the others that are further away. This is a prime AC OG sni pi ng spot. You can see the West door going to B and most windows on the West building. You can also jump down to the corner window of the East building and enter from there. I've used that more times than I can count to flank.
North East of A: Second floor window West side of building: Jump on the awning and down the row. Shoot out the window at the end and jump in the window. Its that easy. Arguably one of the best spots to camp on the map.
WHEN RESPONDING TO THIS POST: do not use words that you would use to search for this kind of post. For these to remain fun you can't encourage many people to use them. I only post them because I have frequented this forum for so long it only seemed appropriate.