Apart from the three energy sources (plus one sexual if it were there), there are other building blocks for a better practice of microcosmic circulation. For ease of exposition, I shall be mixing up concepts from the texts and my own practical experience. Needless to say, anything being unbecoming shall be my fault.
1. Building up a strong centre-line is very important. Not only can it facilitate chi-flow, it can also tune up the weaker side of one's body, for a more aligned structure.
2. The classic concept of bathing (沐浴) is important too (some practitioners say more important than mere circulation, I would say as important as). Its essence is point-meditation, and its purpose is to strengthen the orbit or for a better metaphor, the furnace.
3. A feeling of Muscles as One should be cultivated during meditation. And this feeling can best be cultivated by supplementing Taoist meditation with zhan zhuang or tai-chi chi-kung.
4. A focused mind with mental state between asleep and wake-up is essential throughout the whole practice.
5. An early cultivation of a feeling of a continuous chain will be beneficial for higher level practice.
Note: These points are in addition to relevant points mentioned in other posts.