I agree partially with "Ihatemyself". While it is recommended to opt for known online shops it is equally important to be aware and alert for the threats. I think the following guidelines should be followed for a safer online shopping experience:
1. Check the reputation/popularity of the site (as mentioned earlier).
2. Try to find some reviews on this site.
3. Find out the payment gateway used by the site (like CCAvenue/Paypal etc..). Only trust sites with good payment gateways. CCAvenue provides Verisign approved protection level which is dependable. Some sites use payment gateway provided by Verisign. Verify the validity of the Verisign certificate for the site.
Now steps to be taken care-off at your computer's end:
1. Keep all your softwares (windows/linux/security softwares) updated.
2. Do not keep any unwanted/useless software installed as it may have some bug which might compromise security of your system.
3. Run all security softwares (anti-virus/anti-spyware etc..) regularly and especially before opting for online shopping. You might use multiple security software (if there is no conflict) as no security software is 100% accurate. For example: I generally use Spybot - S&D, Ad-Aware and AVG Anti-spyware simultaneously and all of these softwares catch some or the other spyware(s).
4. Try to avoid accepting cookies.
and finally...
Keep watch on your credit card statement regularly and alert your credit card company immediately if you find any misuse. Your credit company might be able to stop the actual transaction or trace the user.
I have been following these practice for a long time now and have done online shopping more than 100 times without ever facing a problem. Some of the sites I have shopped on includes ebay.in, amazon.com, indiatimes.com, sify.com, yantraonline.in, irctc.co.in, makemytrip.com, yatra.com etc.
So HAPPY SHOPPING!!!