You want to use enough only to heat the tobacco but not to cook or burn it!
Buy packs of circular aluminum pre-cut at the head shop or online specialy made for hookah.
Punching holes, everyone has their own method. Depends on what you like, depends on the cut and smoking quality and quanity.
When laying down the foil, always have the shiny side down to reflect the coals heat into the shisha and not upwards as you will lose heat.
Punch with toothpick, pin, fork etc, or just get the pincher. The bigger the clay bowl, the more holes.
Do not ever light coals directly on top of the tobacco, it will scorch it upon lighting. put the coals around the edges and slowly toward the middle as you smoke.
Try natural coals for no after taste.
hold your coals while lighting in a semi covered aluminum holder in case they explode and fly, also to minimize soot and dust in your room, or best light outside.
Get a wind cover.
if you have a carpet on your floor, or its wood - lay down aluminum foil or buy a large thin piece of flat tin to lay down from falling coals and sparks.