1. Experience. There's not hard and fast rule that declares that "this is enough" or "this isn't enough." Through enough attempts and keeping good records of your workings and of the results you will ultimately be able to figure out how much is needed for any given working.
2. Calling upon external beings to help you (deities, angels, etc.) and using items which have their own energetic charge either inherently (like crystals) or through extended magickal use (such as a trusty old wand you've used many times).
3. Sort of. It is ultimately still you who does the magick, but creating a sigil or some some such will aid you in continuing to work your magick long after the ritual has ended. I once made a sigil just as an example in order to explain sigils to a friend - no spells or rituals or even any conscious intent on my end - and it went ahead and worked anyway. Granted, I wasn't asking for anything difficult or demanding, just unlikely.
4. I unfortunately can't quite figure out what is meant. Could you elaborate?
5. In certain, very specific workings, you need the props listed. This generally only applies to things Hermetic summoning of demons. Beyond that, props are mostly to make things easier or to allow physically striking imagery that causes an emotional, and therefore energetic, response in us.
6. Magick can make any change allowed by the nature of the thing changed. You can use a spell to mend a relationship because relationships are a mendable thing. You can use a spell to hex someone because people are affected by luck and will naturally have extreme bouts of both good luck and bad luck. You cannot use a spell to turn into a cat because metamorphosis between species is not something a human is meant to do.
Magick can therefore only do those things which could theoretically happen on their own, even with extremely low odds.