A question from a fellow grower:
I am a virgin at this. The salesman said to give them 24 light and not start nutrients or co2 for a week so the plants can get acclimated. My question- how long do I do a 24hr light cycles for my clones? When do I change to a 18/6 light cycle.
It kinda depends on the strain. Is it an autoflower strain? It also depends on the “style” or the type of “grow”. The salesman said the first week, I assume, for these clones to have a little time to root in what look like rockwool plugs. If the strain is autoflowering, you could run 18/6 for the rest of the grow. However as most strains need more than 12 hours uninterrupted darkness per day to flower, and most strains will grow about another third their size through flower, you would keep the 18/6 cycle until a little more than half the grow-space has been filled. This will allow room for the plant to continue to grow through the flowering phase without running out of room and becoming too crowded – which could lead to mold or bud rot or burnt parts of the plant where it grows into the lights.,
Very good advice to judge when to begin flowering, by observing how much space is left in your grow area. 
Most of the time Clones are vegged froma minimum 2 weeks all the way to a full 8 weeks.
As far as nutrients; All you need to remember is that it is not necessary to feed nutrients to the plant until there is an established root zone.
I would advise you to use a 20/4 light photperiod for clones. All plants need some rest. This will also allow some minimal stretching to occur during veg, so that it all does go leggy on you, when you induce flowering 12/12.
Good Luck. More info from you as far as strain, etc…would allow us to give you a more educated response. Peace
I simply adore how most of us intuit that the planet needs ‘rest’. This is an overwhelming impulse in my mind. I think it must be because, when a question arises in my mind, I always think of the plants ancestors. Not that every, even universal, intuitions are always correct, but, hey, intuitions don’t arise from nothing, but arise distilled from out collective knowledge and experience. I’ve learned to trust mine. ‘Trust, but verify’ a great senile, probably crapping in his diaper President once read off his teleprompter.