I am doing majority of my online shopping from Amezon, Flipkart and Paytm mall. My strategy of online shopping is as under.
Do the survey of availability of the product which you want to buy.
Compare the discount between all the online shopping sites.
Go on the best discounted website.
Check the review of that product from that specific website.
Check the dealer who will be delivering the product through the specific site.
Check the return policy of that product.
If everything above mentioned is trust worthy then finally buy the product.