I got stuck on this when I first started, I'll answer each bit in the same order you asked.
1. Use any candle colour you like, if you want to use candles that is.
2. It doesn't matter it's colour.
3. Some people do 4 Points, some do 5, I do 3. So, up to you entirely.
4. Where you want to, some like having the incense inside the circle, some like to burn it outside, but most I have heard and done myself is inside the circle.
5. Blow it out, snuff it with a candle snuffer, it's up to you.
1. Lavender is generally good for Psychic Enhancement, Attracting Men and Women, Luck, Purification, Spiritual Aspects etc.
2. However you like, since incense doesn't burn long, leave it till it's done, but, if your rite finishes before the incense burns out - put it out, you can reuse it.
3. Generally speaking, if you're going to use Candles in a Circle, you light them as you call each of the Spirits/Elements/Powers etc to your aid, to signify that they have arrived or that this is where they are meant to be. And then you blow them out at the end as you farewell each of the Powers that you called to your aid, Do you have to remain in the circle for the whole rite? Yes, however, if say an emergency happens or the phone rings etc - it is polite to let the powers that you have called know that you have to move away for a bit and always nice to bring them back a little offering for their patience (Added to what offering you're already giving them)
You don't have to wait for everything to go out, as I mentioned before.