Sweden begins with the Grand Campaign surrounded by an alliance that is de facto organized against it: Denmark, Poland-Lithuania, and Russia. In addition to these enemies, Prussia is historically unfriendly (although thankfully it cannot do much in the beginning to actually cause Sweden harm), and Courland tends to declare war on Sweden within the first few turns. Those who like Sweden—namely Great Britain, France, and the Ottoman Empire—are too far away to be of much assistance. Therefore, Sweden is largely on its own from the get-go.
Sweden’s advantage is the relative quality of its armies over those of its rivals. Most of Poland-Lithuania’s army in 1700 consists of pikemen and militia, which aren’t of much threat against Sweden’s capabilities; Russia makes do with inferior cavalry and largely inferior infantry; Denmark’s army is paltry at best and consisted almost entirely of militia and provincial cavalry.
Probably Sweden’s best course of action is to neutralize Denmark as quickly as possible. Aside from Poland-Lithuania and Russia (which are almost certain to declare war on Sweden regardless), Denmark is diplomatically isolated; its lands are rich and Protestant, it has a college which can grant Sweden an edge in research; its fleet can be easily defeated and incorporated into the Swedish navy, granting it dominance in the Baltic Sea. Peace can be made with Denmark after it is isolated in Iceland; failing that, taking Iceland can create a useful stepping stone into India or the Americas.
In the meantime, Sweden’s armies to the east will need defending. It will face attacks from Russia, Poland-Lithuania, and perhaps Courland. After the situation in the west is dealt with with Denmark's hopefully swift demise, Sweden can focus its full efforts on wiping out Poland-Lithuania and its rich lands, or vast Russia. Russia's harder to kill but more isolated, while Poland-Lithuania can be broken with effort but puts Sweden within the borders of Austria and Prussia. After Sweden's three traditional enemies are wiped out, the world is its oyster.