1) As far as Bitcoin is concerned I really doubt that there is any right time. Because it could happen that current price may be the lowest price or it could also happen that it may be the highest price.
2) I would say keep purchasing small qty at regular times. Afterall, if your from India still there is no clarity about Bitcoin currently.
3) Unocoin and BTCXINDIA are the most reliable at present. Service and quickness wise BTCXINDIA stands out among the rest.
4) If you would be purchasing smaller quantity you can store it among the blockchain itself. But once you have few BTC it is advisable to store it offline.

Also if you would like to buy/sell BTC you can contact me via PM or follow  https://bitcointalk.org/index.php?topic=837811.20