These require care when handling if you are not to cause yourself great discomfort. The juice stings intensely so avoid rubbing your eyes or nose after cutting or handling a chilli. I find preparing chillies under cold running water helps, but care is still the best course of action. If you have sensitive skin, wear a pair of rubber gloves.
To deseed a chilli, use a paring knife to slice it open, then use the tip of the knife to scrape out the seeds under running cold water. Chop or slice the chilli as finely as required.