I have ~400 multikills with the javelin, and a lot of these spots helped me get there. I never really knew about the one on sub base, I normally just shot it from the crates on the other side of A. On terminal, you can also shoot it by the crates(where people boost) to the overhang above C, you should see a black dot and try to aim right below it or on it.
for salvage, you can aim to C from B, and you can also aim to B on salvage from where B would be in search.
a lot of the other maps are pretty much just aim and shoot and cross your fingers. for wasteland, you can go around the hedge and aim at the tunnel entrance by b, or any other flag and get a multi kill every time. on skidrow you can aim for the stairs (where most snipers snipe through B) and then walk outside and shoot it. on afghan you can go to the first bunker and aim it to the top of the cliff or to the pipes (to the right of the cliff, towards B)
I wish i had a hd pvr to record some of my spots,