There is no proven method of influencing the dreams of another person. However, it may be possible to increase the likelihood that someone dreams about you simply by being an active and noticeable part of that person's waking life.
Scientific theories differ about the ultimate purpose of dreaming, but it is generally agreed that what happens during the daytime can have a big influence on dream content. Being stressed about something in waking life probably increases the likelihood of having stressful dreams. While dreams often include elements that seem to be completely random, even an absurd dream will often contain memories or thoughts that can be traced to the dreamer's waking life.
However, the specific content of any particular dream is typically beyond the dreamer's control. According to Psychology Today, while there is some evidence that post-hypnotic suggestions can be used to influence dream content, and that some people are capable of directing some of their own dream content through a technique called "lucid dreaming," these techniques only work in a small proportion of individuals, and they only work if the dreamer is an active and willing participant in the process.
In the final analysis, the best way of encouraging a person to dream about you is to become an important part of his waking life. If a person thinks about you a lot while awake, he will probably also dream about you.