trim only the larger meduim fan leaves that are covering buds or buds on other plants, i started with low 2,s some trim far too much, but the big fan leaves helps the plant to produce sugars which results in a better plant, trim any low ones not near bud,brown or burnt ones and any in the way of bud or other plants, always leave as much as possible, and check and trim at least once a week as they will grow and more leaves may cover, the trick is leave the smaller and med leaves unless brown or burnt, and only take off what is in way of buds or other plants, the more you leave the better the result, but i usually do a small small trim each week, when they only have a week or so left, then take all the large/medium leaves with NO crystal, leaving just the small ones in the bud, this helps the light get right in for the last week, but till then, keep as many as you can, you wouldnt remove your lungs so dont your plants, just those in way!