After generating aspiring bodhicitta before the guru and the Three Jewels - which means wanting to benefit all sentient beings and become enlightened in order to accomplish that - one should observe eight precepts in order to protect one's altruistic intention from degenerating in this and future lives.
How to protect your altruistic intention from degenerating in this life:
1. Remember the advantages of bodhicitta again and again.
2. To strengthen one's bodhicitta, generate the thought to attain enlightenment for the benefit of all sentient beings three times in the morning and three times in the evening. Recitation and contemplation of the prayer for taking refuge and generating the dedicated heart (previously sent) is a good way to fulfil this.
3. Do not give up working for sentient beings even when they are harmful.
4. To enhance one's bodhicitta, accumulate both merit and wisdom continuously. After generating aspiring bodhicitta before the guru and the Three Jewels, one should observe eight precepts in order to protect one's altruistic intention from degenerating in this and future lives.
How to protect yourself from being separated from bodhicitta in future lives:
Abandon the four 'black actions':
1. Deceiving the guru, abbot or other holy beings with lies.
2. Causing others to regret virtuous actions that they have done.
3. Abusing or criticizing bodhisattvas or the Mahayana (Mahayana is the "Great Vehicle" of Buddhism).
4. Not acting with a pure selfless wish but with pretention and deceit.
Practice the four 'white actions':
1. Abandon deliberately deceiving and lying to gurus, abbots and so forth.
2. Be straightforward, without pretension or deceit.
3. Generate the recognition of bodhisattvas as one's teacher and praise them.
4. Assume the responsibility oneself to lead all sentient beings to enlightenment.