Here is how you can get driving directions (street to street) in Bangalore!
Go to MapmyIndia. Click on Directions and enter the from and to addresses. This will give you complete street by street directions to get to your destination. Currently this site does not offer door to door directions though. So once you reach your destination street you will still have to ask around or get further directions.
This site can be used for city to city driving directions for anywhere in India.
Using BTIS (Bangalore-specific)
Go to BTIS and click on Directions. This site provides you similar driving directions to any destination in Bangalore. Here you are restricted to only localities instead of specifying streets. Airtel cellular customers can also use their cell phones to query directions, although this is a bit cumbersome as you have to enter locality names correctly.
Please note that these websites will not completely solve your problem! You will still need to get directions from the destination street to the exact address that you are traveling to. So either ask around once you reach the street or call the people you are visiting.