where to start?

[Smoker06]

Can you ruin a cigar by not lighting it correctly?

I don't think you can ruin it, but you can make it less enjoyable.

If you hold the flame to the foot and puff away, you're likely to char the foot and the first puffs might be harsh and/or bitter. Eventually this will go away.

If you don't light the foot completely and evenly, you might cause an uneven burn or even a runner or canoe. But a well made, properly stored cigar will eventually even itself out.