I collected a few exploits for 1.6, with those you can plant the bomb hidden, quietly and partially unattainablly for other players.
On dust you have to practise a bit. It is really hard to get on the big crate. Some dudes say this is not possible but they suck, it IS. If you don't believe I can make a demo. Once you up there plant the bomb und run. The CT is in 99,9% of the cases not able to come up there. Even if he can, mostly it is too late.
At Bombsite A you must jumb in a circle to get to the other side. Then you can plant it. Some players dont know this and think the bomb is invisible. The funny thing is, you are allowed to do this in cups, too, because you can get there on your own. So this is LEGAL.
Silent plant: (not legal in cups)
dust2. Directly duck over the corner in de_dust2, bombsite A. Just plant and no1 will hear the bomb ticking.
inferno. The bombsite after banana. Position yourself as in the picture. Plant and again nobody will hear the bomb ticking.
nuke. The upper bombsite. Place yourself as in the picture and plant. Nobody will hear the bomb AND nobody will see the red light, beacuse it is quite hidden.