Driving habits

I heard the following tips from my friends. Are they true?

1. We should switch on the A/c after the engine gets heated somewhat like atleast driving for a KM or so to increase the cooling effciency and the mileage.

2. After starting we should avoid taking reverse. We should first engage the first gear and move the car a bit, and then only engage the reverse and reverse the car to get hassle free gear shift and longer life of gearbox.

Moving the car forward or back should not effect much unless you press the gas too hard. What I think about moving back first is somewhat related with personal believe as I have seen many long distance bus drivers to do that first for few feet and then engage the reverse when the driver changes at the dhabas. they believe that directly moving back is unlucky and bad, without any solid reason. I may be wrong, but I have seen that and feel like this.