Basic Passing Concepts ...
Passing the Guard:
First Rule of Passing: Don't die! That is - don't be swept, armbarred or choked. Spend some time in Guard survival training. Don't pass - just survive. Let your oponent do his best to attack. Just survive. Become competent at that first. Many people are so focussed on where they want to end up or on what pass they want to do, that they forget that their opponent has his own 'evil plans' as well. Spend a large portion of your attention on not getting 'caught out'!
Second Rule of Passing: Realise that our passing needs to be '3 dimensional'! By this I mean that our passing strategies should include passing low and tight, high and fast, go around, go through, go under - whatever it takes. It is a common mistake to become locked into a one dimensional passing style (eg: passing low and to the left) - of course, this then only requires a one dimensional guard from our opponent and we are in trouble.
In short, if he has a one dimensional type of Guard and our passing is more three dimensional - we tend to pass - and vica versa.
Third Rule of Passing: remember, the onus is one the opponent to finish or sweep you - not for you to pass. So don't panic - you are on top - and you have the advantage of being able to apply your weight - he does not. As my friend David Meyer likes to say - "the one thing you have got going for you, even when you are dead - is your weight! For a while anyways!"
Hope this helps - broad outlines only.