Roppongi, Shibuya, Ebisu, Shinjuku, Marunouchi are some good areas..
Roppongi, Shibuya, Ebisu, Shinjuku, Marunouchi are some good areas where you can meet or bump into foreigners. A971 - near midtown, PinkCow Club very near to Roppongi square, Oakdoor (in Hyat)
PCM - Marunouchi - http://www.miyoshi-grp.com/cardinal/pcm/index.html
PCA - Akasaka - http://www.miyoshi-grp.com/cardinal/pca/index.html
A971 - http://www.cafecompany.co.jp/brands/a971/index.html
Hogoblin chain of pubs - http://hobgoblin.jp/
are some places where you can hang around with foreigners.
In case you are an Indian and want to meet new Indian friends you might want to try out Swagat Roppongi (www.swagat-jp.com) where you can just talk across to anybody and get acquainted.
In places like Ginza or some traditional places, knowing some Japanese helps. Else the restaurant owner or hall staff fear embarrasment (of not speaking English) and hence might just refuse entry to the place. In such cases its not any racist or foreigner unfriendly behavior but the fear of not able to serve you or talk /understand you is more and hence the refusal.