I have been to Goa some 15 times. Please keep in mind, Goa although small in area is still a state and has lots to offer than just beaches but yes, most people come to Goa for beach, party and cheap beer. If that is you want then 3-4 days are enough. If its your first time, I would suggest you go to North Goa - good old Calangute beach as you will be closer to few other beaches and capital Panaji (Panjim) where you can ride and visit few heritage, history (Portuguese) etc. You can visit Chapora fort - Dil chahata hai movie and Fort Aguada by scooter. There are lots of night party places around Calangute. South Goa is bit different, quiet, serene, hills and if you happen to be there on Saturday then you can enjoy Silent Noise - Headphone party as well. Enjoy your trip! I can go to Goa anytime even on monsoons but best time to go is from mid-October and before early March although late September and March/April/May are also okay but it gets too hot. Avoid December as it gets too crowded and expensive. Other than beaches you can see forts, waterfall(Doodhsagar), Temples, Church's and national parks. Enjoy your trip!
Hi Priyesh, The best time to visit Goa is between November and March when the Goa weather is beautifully balmy & clear with a cool sea breeze blowing through. The least you should plan for is 3 days: 1 day each for North Goa & South Goa, and one day for shopping and relaxing on a beach. If you have more time, keep 2 days for North Goa, 2 days for South Goa, and 1 day for shopping/beach. That's sufficient on all accounts.