Starting off with shimano gears I am completely new to multi gear bikes, the last time i rode a bike was in 1965.
My question, what gear combination do i need to start off on level ground.
If i try to back pedal just a bit, to get the pedals at 12 and 6 o' clock to get maximum leverage to start off, the gears won't let me do it.
What combination will let me back up the pedals?
Thanks,
Mike
You need to be moving (and pedalling) to change gears on a bike with derailleurs. So you should try to change down before stopping, to a small gear at the front and a big gear at the back.  The front gear are often labelled L...H for low to high, while the back gears are 1...8 (or anywhere between 5 and 11 depending on how many cogs you have) -- again low to high.  

If you try to select a different gear and then backpedal before it engages the drive train can lock up; this is probably why you can't backpedal if you changed down without pedalling forwards.  You can lift the back wheel and spin the pedals in the normal forward direction (by foot or hand, whatever's easier) to change gear while stationary.