Vampire strategy seems to emphasize infiltration, exploitation, and then destruction of a host population. Vampires try to seed themselves and their minions into large societies where they can blend in. Once there, they convert many to their side and slowly gorge themselves off the psychic and latent life energies of the area. Finally, before risking exposure, the Vampires will conspire to destroy the host city/society to keep their presence a secret.
Vampiric weaknesses are still present, though some are more or less exaggerated in fiction and myth. Sunlight is indeed a real threat to vampires, surprisingly. Ultraviolet light apparently mixes poorly with some chemicals present in Vampiric physiology, more so in their exoskeleton than in other systems, which means stronger Vampires are actually more greatly affected by sunlight exposure. Their circulatory system also reacts poorly to the presence of silver-based chemicals, leading to their popular use by monster hunters. Their aversion to running water is an exaggeration. Vampires, like many insects, hate salt water for practical reasons, so living near the ocean or having salt and water on hand is a great way to irritate them, but their weakness only goes so far. Similarly, their inability to enter uninvited into a home is a total fabrication, possibly by vampires themselves.
On the other hand, stabbing a vampire in the heart is a very useful tactic. It appears their heart serves as both the center of their circulatory system, and as a major node in their nervous system. This may account for why blood consumptions seems to increase their reflexes and stamina so quickly, but it also means paralysis if the heart is arrested. Also, holy symbols do actually work. It is theorized that the mental process of belief and hope, in the presence of a holy symbol and extreme terror, create a very unappetizing psychic feedback that can repel a Vampire who is unprepared for it.