Holding the Charge:
In most cases, if you don’t discharge a touch spell on the round you cast it, you can hold the charge (postpone the discharge of the spell) indefinitely. You can make touch attacks round after round. If you cast another spell, the touch spell dissipates.
That means that missing on the touch attack doesn't (typically) cause the spell to fail. Rather, the spell's energy stays on your hand (or other relevant appendage) until it's discharged in some way.
So, if you cast Shocking Grasp then miss on the touch attack, you can try to touch an enemy in the next round (or as part of an Attack of Opportunity). And, you can keep trying until one of the following happens: you successfully hit an opponent, you accidentally touch something, you cast another spell, or you choose to dismiss the spell energy.
- Cast Shocking Grasp successfully, roll a touch attack, miss
- enemy walks away, provoking an Attack of Opportunity: roll a touch attack, miss again
- walk up to enemy, roll a touch attack, miss again (your luck is horrible)
- enemy walks away again, provoking an Attack of Opportunity: roll a touch attack, hit (yay!), do damage
As for touching 6 friends with one spell in one round, that's just what the rules say: if you're casting a spell that requires you touch your friends for them to benefit, the rules are giving you an explicit limit on the number of such friends you can touch in a single round. The assumption is that your friends are helping by bunching up a bit and reaching out a hand (or other appropriate appendage) for you to reach out and touch.
Note, however, that the SRD entry for range "touch" says that
You can touch as many willing targets as you can reach as part of the casting, but all targets of the spell must be touched in the same round that you finish casting the spell.
... which probably means that your friends have to be within your reach when you cast the spell (ie., adjacent to you, unless you have natural reach somehow) to be touched, but that you can hit as many of them as you want (again, on the assumption that they're helping - or, at least, not trying to avoid your touch).