Kaggle - Chang's comment in Kaggle forum
Just manual tuning, tune feature_fraction, bagging_fraction, min_data_in_leaf (or min child weight), lambda_l2, lambda_l1 by order with high learning rate, then tune the num_leaves and adjust learning rate to lower one.
下に書いたパラメータを手動チューニング、その際learningrateは高めに設定する。その後num_leavesを調整しつつlearning rateを下げる