How did Japanese foreign policy change over the 1800s and early 1900s?

As you have not specified when in the 1800s, I will start from Tokugawa.

The beginning of the 1800s the policy started out as control and separation. Foreigners were only allowed to enter Japan through Nagasaki and most of their actions were heavily restricted. This was done as their influence was deemed as a threat to the tenuous but surprisingly long-lived Tokugawa power structure.

As 1852 came and Matthew Perry militarily forced japan to accept outsiders, the policy shifted to appeasement and a form of submission. Japan tried to keep its honor but it repeatedly caved into demands from the west. Many Japanese were appalled at the percieved loss of honor and picked fights with better armed western fleets. This anger combined with a large number of other grieveances led to the Meiji restoration in 1868.

As the Meiji government took power they changed the foreign policy, however this change was very subtle. No longer was Japan submitting to foreign powers, it was encouraging the introduction of foreign ideas. Less out of a feel of surrender and weakness, rather to gain the knowledge of the west to someday cast off its influence and stronghold over Asia. Japan brought in various advisors from all over Europe and America. The French and the Germans were sued for military, the U.S. for it's infrastructure and travel skills, and so on.

In the very late 1800s and early 1900s, as Japan grew stronger and stronger, it outgrew the need for the Western advisors and powers. This lead to a growing rejection of the West, yet still and underlying fear of it. Japan also felt like it had replaced China as the head of Asia. Chian at this time was ravaged by repeated skirmishes with European militaries, massive corruption and a breakdown of its economic and social structure. Japan took the western created ideas of Total Warfare and Colonialism and began to set its sights on North China and its massive amounts of resources. After it has successfully defeated China in 1895, the European powers "stepped in" and forced Japan to return the land it had gained. This was a national embarrassment, and Japan vowed to reclaim the land and more.

Japan once again found itself at war, not with a small Asian power, but with Russia. Japan narrowly (by a stroke of luck and darn good timing) won the war in 1905. Japan had now cemented itself on the world stage and proven to most within the country that Japan was above the need for the Western Countries. Thsi combined with the embarrassment and and the fear of Western Power caused Japanese antionalism to surge and surge.

This surge kept on strenthening and led to Japan's actions on China in 1937 all the way to the bombing of Pearl harbor.