brokers galore!

Being a newbie to trading shares and also a newbie to this forum I was hoping to get some advice or reviews from this community who are obviously more knowledgeable than me.
Over the past week i've been looking at brokers and trying to compare them,but seem to be going around in circles.It seems that Comsec is the 'Manchester United' of the stockbrokers and seem to be everywhere i turn but are they the best?
Whilst also looking at CMC and Bell Direct who also seem to be good from looking at their websites.
Price of trading isnt much of an issue but useability for a new trader like me is essential.Looking at demos Bell Direct seem to be easy enough to navigate,although there's no way of really telling unless you sign up.

But my questions are:

1.Do you have to have a linked account with that broker? e. Commsec requires you to have a CBA account along side.Or can you use your own savings account?
2.Are you able to trade on overseas markets through these Australian brokers?
3.Are you charged more for trading overseas?
4.Which is the easiest to navigate?